785 research outputs found
Sticking lifetime of ultracold CaF molecules in triplet interactions
A six-dimensional potential energy surface is constructed for the
spin-polarized triplet state of CaF-CaF by \textit{ab initio} calculations at
the CCSD(T) level of theory, followed by Gaussian process interpolation. The
potential is utilized to calculate the density of states for this bi
alkaline-earth-halogen system where we find the value 0.038 K,
implying a mean resonance spacing of 26 K in the collision complex. This
value implies an associated Rice-Ramsperger-Kassel-Marcus lifetime of 18
s, thus predicting long-lived complexes in collisions at ultracold
temperatures
Conductivity landscape of highly oriented pyrolytic graphite surface containing ribbons and edges
We present an extensive study on electrical spectroscopy of graphene ribbons
and edges of highly oriented pyrolytic graphite (HOPG) using atomic force
microscope (AFM). We have addressed in the present study two main issues, (1)
How does the electrical property of the graphite (graphene) sheet change when
the graphite layer is displaced by shear forces? and (2) How does the
electrical property of the graphite sheet change across a step edge? While
addressing these two issues we observed, (1) variation of conductance among the
graphite ribbons on the surface of HOPG. The top layer always exhibits more
conductance than the lower layers, (2) two different monolayer ribbons on the
same sheet of graphite shows different conductance, (3) certain ribbon/sheet
edges show sharp rise in current, (4) certain ribbons/sheets on the same edge
shows both presence and absense of the sharp rise in the current, (5) some
lower layers at the interface near a step edge shows a strange dip in the
current/conductance (depletion of charge). We discuss possible reasons for such
rich conducting landscape on the surface of graphite.Comment: 13 pages, 9 figures. For better quality figures please contact autho
Soft chemical routes to semiconductor nanostructures
Soft chemistry has emerged as an important means of generating nanocrystals, nanowires and other nanostructures of semiconducting materials. We describe the synthesis of CdS and other metal chalcogenide nanocrystals by a solvothermal route. We also describe the synthesis of nanocrystals of AlN, GaN and InN by the reaction of hexamethyldisilazane with the corresponding metal chloride or metal cupferronate under solvothermal conditions. Nanowires of Se and Te have been obtained by a self-seeding solution-based method. A single source precursor based on urea complexes of metal chlorides gives rise to metal nitride nanocrystals, nanowires and nanotubes. The liquidliquid interface provides an excellent medium for preparing single-crystalline films of metal chalcogenides
InN nanocrystals, nanowires, and nanotubes
Various chemical methods have been utilized to prepare InN nanocrystals, nanowires and nanotubes, which have been characterized by several techniques (see TEM images). The nanostructures exhibit an absorption band in the near-IR region at around 0.7 eV, which rather than being caused by defects, is shown to be an intrinsic and characteristic feature of InN
The Influence of Building Structure on Human Perception in Interior Spaces
Structures create interior spaces. However, the sense of every space depends on the type of structure used. This paper tries to evaluate structural systems apply in architecture and then analyse space identity given by different structures. The method of this study mainly depends on a survey in the current literature and case study which the colour building in the department of architecture in EMU-North Cyprus has taken as the case study. Frame concrete (column and beam) is used in the building, which has made the interiors compacted in the structure's boundary. At the same time, inside spaces have some freedom as partition walls separate them. In this case, the structure proliferates visual focal points, corners and angles, to the main space. These visual definitions lately make the spaces to be more defined
A Combination Theorem for Metric Bundles
We define metric bundles/metric graph bundles which provide a purely
topological/coarse-geometric generalization of the notion of trees of metric
spaces a la Bestvina-Feighn in the special case that the inclusions of the edge
spaces into the vertex spaces are uniform coarsely surjective quasi-isometries.
We prove the existence of quasi-isometric sections in this generality. Then we
prove a combination theorem for metric (graph) bundles (including exact
sequences of groups) that establishes sufficient conditions, particularly
flaring, under which the metric bundles are hyperbolic. We use this to give
examples of surface bundles over hyperbolic disks, whose universal cover is
Gromov-hyperbolic. We also show that in typical situations, flaring is also a
necessary condition.Comment: v3: Major revision: 56 pages 5 figures. Many details added.
Characterization of convex cocompact subgroups of mapping class groups of
surfaces with punctures in terms of relative hyperbolicity given v4: Final
version incorporating referee comments: 63 pages 5 figures. To appear in
Geom. Funct. Ana
Depth-Resolved Multispectral Sub-Surface Imaging Using Multifunctional Upconversion Phosphors with Paramagnetic Properties
Molecular imaging is very promising technique used for surgical guidance, which requires advancements related to properties of imaging agents and subsequent data retrieval methods from measured multispectral images. In this article, an upconversion material is introduced for subsurface near-infrared imaging and for the depth recovery of the material embedded below the biological tissue. The results confirm significant correlation between the analytical depth estimate of the material under the tissue and the measured ratio of emitted light from the material at two different wavelengths. Experiments with biological tissue samples demonstrate depth resolved imaging using the rare earth doped multifunctional phosphors. In vitro tests reveal no significant toxicity, whereas the magnetic measurements of the phosphors show that the particles are suitable as magnetic resonance imaging agents. The confocal imaging of fibroblast cells with these phosphors reveals their potential for in vivo imaging. The depth-resolved imaging technique with such phosphors has broad implications for real-time intraoperative surgical guidance
Fabrication of Nd3+ and Yb3+ doped NIR emitting nano fluorescent probe: A candidate for bioimaging applications
The intentional design of rare earth doped luminescent architecture exhibits unique optical properties and it can be considered as a promising and potential probe for optical imaging applications. Calcium fluoride (CaF2) nanoparticles doped with optimum concentration of Nd3+ and Yb3+ as sensitizer and activator, respectively, were synthesized by wet precipitation method and characterized by x-ray diffraction (XRD) and photoluminescence. In spite of the fact that the energy transfer takes place from Nd3+ to Yb3+, the luminescence intensity was found to be weak due to the lattice defects generated from the doping of trivalent cations (Nd3+ and Yb3+) for divalent host cations (Ca2+). These defect centres were tailored via charge compensation approach by co-doping Na+ ion and by optimizing its concentration and heat treatment duration. CaF2 doped with 5 mol% Nd3+, 3 mol% Yb3+ and 4 mol% Na+ after heat treatment for 2 h exhibited significantly enhanced emission intensity and life time. The ex vivo fluorescence imaging experiment was done at various thickness of chicken breast tissue. The maximum theoretical depth penetration of the NIR light was calculated and the value is 14 mm. The fabricated phosphor can serve as contrast agent for deep tissue near infrared (NIR) light imaging
Sol–gel preparation of low oxygen content, high surface area silicon nitride and imidonitride materials
Reactions of Si(NHMe)4 with ammonia are effectively catalysed by small ammonium triflate concentrations, and can be used to produce free-standing silicon imide gels. Firing at various temperatures produces amorphous or partially crystallised silicon imidonitride/nitride samples with high surface areas and low oxygen contents. The crystalline phase is entirely ?-Si3N4 and structural similarities are observed between the amorphous and crystallised materials
FSPVDsse: A Forward Secure Publicly Verifiable Dynamic SSE scheme
A symmetric searchable encryption (SSE) scheme allows a client (data owner)
to search on encrypted data outsourced to an untrusted cloud server. The search
may either be a single keyword search or a complex query search like
conjunctive or Boolean keyword search. Information leakage is quite high for
dynamic SSE, where data might be updated. It has been proven that to avoid this
information leakage an SSE scheme with dynamic data must be forward private. A
dynamic SSE scheme is said to be forward private, if adding a keyword-document
pair does not reveal any information about the previous search result with that
keyword.
In SSE setting, the data owner has very low computation and storage power. In
this setting, though some schemes achieve forward privacy with
honest-but-curious cloud, it becomes difficult to achieve forward privacy when
the server is malicious, meaning that it can alter the data. Verifiable dynamic
SSE requires the server to give a proof of the result of the search query. The
data owner can verify this proof efficiently. In this paper, we have proposed a
generic publicly verifiable dynamic SSE (DSSE) scheme that makes any forward
private DSSE scheme verifiable without losing forward privacy. The proposed
scheme does not require any extra storage at owner-side and requires minimal
computational cost as well for the owner. Moreover, we have compared our scheme
with the existing results and show that our scheme is practical.Comment: 17 pages, Published in ProvSec 201
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