9,576 research outputs found
Topography-based flow-directional roughness: potential and challenges
Abstract. Surface texture analysis applied to high-resolution digital terrain models (HRDTMs) is a promising approach for extracting useful fine-scale morphological information. Surface roughness, considered here as a synonym of surface texture, can have a discriminant role in the detection of different geomorphic processes and factors. Very often, the local morphology presents, at different scales, anisotropic characteristics that could be taken into account when calculating or measuring surface roughness. The high morphological detail of HRDTMs permits the description of different aspects of surface roughness, beyond an evaluation limited to isotropic measures of surface roughness. The generalization of the concept of roughness implies the need to refer to a family of specific roughness indices capable of capturing specific multiscale and anisotropic aspects of surface morphology. An interesting set of roughness indices is represented by directional measures of roughness that can be meaningful in the context of analyzed and modeled flow processes. Accordingly, we test the application of a flow-oriented directional measure of roughness based on the geostatistical bivariate index MAD (median of absolute directional differences), which is computed considering surface gravity-driven flow direction. MAD is derived from a modification of a variogram and is specifically designed for the geomorphometric analysis of HRDTMs. The presented approach shows the potential impact of considering directionality in the calculation of roughness indices. The results demonstrate that the use of flow-directional roughness can improve geomorphometric modeling (e.g., sediment connectivity and surface texture modeling) and the interpretation of landscape morphology
Electric motor wheel assembly
A motor wheel assembly with a radial flux brushless electric motor with a seat on the stator interrupting the sequence of stator electromagnets suitabel for housing a caliper of a braking system
What are we going to do about a problem like polymer chemistry? Develop new methods of delivery to improve understanding of a demanding interdisciplinary topic
Following collaboration between two chemistry lecturers and an academic developer an attempt was made to enhance the learning of students within a chemistry module through the adaptation of the delivery of content material. This paper reports a piece of practitioner led research which considered how effective the approach developed was upon the level of student understanding and the process through which this occurred. The module delivery was altered from an emphasis on the transmission of knowledge through a traditional lecture format, to rotating small group problem based sessions and the use of concept maps. Student feedback and higher grades achieved appear to demonstrate it was effective
Spin-orbit-enhanced Wigner localization in quantum dots
We investigate quantum dots with Rashba spin-orbit coupling in the
strongly-correlated regime. We show that the presence of the Rashba interaction
enhances the Wigner localization in these systems, making it achievable for
higher densities than those at which it is observed in Rashba-free quantum
dots. Recurring shapes in the pair-correlated densities of the yrast spectrum,
which might be associated with rotational and vibrational modes, are also
reported.Comment: 5 pages, 4 figure
Colloidal CuFeS2 Nanocrystals: Intermediate Fe d-Band Leads to High Photothermal Conversion Efficiency
We describe the colloidal hot-injection synthesis of phase-pure nanocrystals
(NCs) of a highly abundant mineral, chalcopyrite (CuFeS2). Absorption bands
centered at around 480 and 950 nm, spanning almost the entire visible and near
infrared regions, encompass their optical extinction characteristics. These
peaks are ascribable to electronic transitions from the valence band (VB) to
the empty intermediate band (IB), located in the fundamental gap and mainly
composed of Fe 3d orbitals. Laser-irradiation (at 808 nm) of an aqueous
suspension of CuFeS2 NCs exhibited significant heating, with a photothermal
conversion efficiency of 49%. Such efficient heating is ascribable to the
carrier relaxation within the broad IB band (owing to the indirect VB-IB gap),
as corroborated by transient absorption measurements. The intense absorption
and high photothermal transduction efficiency (PTE) of these NCs in the
so-called biological window (650-900 nm) makes them suitable for photothermal
therapy as demonstrated by tumor cell annihilation upon laser irradiation. The
otherwise harmless nature of these NCs in dark conditions was confirmed by in
vitro toxicity tests on two different cell lines. The presence of the deep Fe
levels constituting the IB is the origin of such enhanced PTE, which can be
used to design other high performing NC photothermal agents.Comment: 12 pages, Chemistry of Materials, 31-May-201
Genetic drift at expanding frontiers promotes gene segregation
Competition between random genetic drift and natural selection plays a
central role in evolution: Whereas non-beneficial mutations often prevail in
small populations by chance, mutations that sweep through large populations
typically confer a selective advantage. Here, however, we observe chance
effects during range expansions that dramatically alter the gene pool even in
large microbial populations. Initially well-mixed populations of two
fluorescently labeled strains of Escherichia coli develop well-defined,
sector-like regions with fractal boundaries in expanding colonies. The
formation of these regions is driven by random fluctuations that originate in a
thin band of pioneers at the expanding frontier. A comparison of bacterial and
yeast colonies (Saccharomyces cerevisiae) suggests that this large-scale
genetic sectoring is a generic phenomenon that may provide a detectable
footprint of past range expansions.Comment: Please visit http://www.pnas.org/content/104/50/19926.abstract for
published articl
Correction of sun glint effect on MIVIS data of the Sicily campaign in July 2000
To assess the suspended and dissolved matter in water in the visible and near infrared spectral regions it is necessary
to estimate with adequate accuracy the water leaving radiance. Consequently radiance measured by a remote
sensor has to be corrected from the atmospheric and the sea surface effects consisting in the path radiance
and the sun and sky glitter radiance contributions. This paper describes the application of the sun glint correction
scheme on to airborne hyperspectral MIVIS measurements acquired on the area of the Straits of Messina
during the campaign in July 2000. In the Messina case study data have been corrected for the atmospheric effects
and for the sun-glitter contribution evaluated following the method proposed by Cox and Munk (1954,
1956). Comparison between glitter contaminated and glitter free data has been made taking into account the radiance
profiles relevant to selected scan lines and the spectra of different pixels belonging to the same scan line
and located out and inside the sun glitter area. The results show that spectra after correction have the same profile
as the contaminated ones, although, at this stage, free glint data have not yet been used in water constituent
retrieval and consequently the reliability of such correction cannot be completely evaluated
Next-to-leading order QCD predictions for the hadronic +jet production
We calculate the next-to-leading order(NLO) QCD corrections to the
production in association with a jet at hadron colliders. We study the impacts
of the complete NLO QCD radiative corrections to the integrated cross sections,
the scale dependence of the cross sections, and the differential cross sections
(, ) of the final -,
Higgs-boson and jet. We find that the corrections significantly modify the
physical observables, and reduce the scale uncertainty of the LO cross section.
Our results show that by applying the inclusive scheme with and taking , , the
K-factor is 1.15 for the process at the Tevatron,
while the K-factors for the processes and
at the LHC are 1.12 and 1.08 respectively. We conclude that to understand the
hadronic associated production, it is necessary to study the NLO QCD
corrections to production process which is part of the inclusive
production.Comment: 26 pages, 27 figures, accepted by Phys. Rev.
Multiscale integration of satellite, airborne and field data for Mediterranean vegetation studies in the natural area of the Castelporziano Estate (Rome)
new experimental approach to land analysis has recently been developed, based on the integration of information
acquired on different scales; it enables the structure and the functionality of the vegetation in natural ecosystems
to be analysed. This research aims at assessing the potentiality of the experimental approach by the integration
of airborne and satellite remotely sensed data with ground measurements of structural parameters. In July
1999 a joint campaign for the acquisition of airborne (MIVIS, spatial resolution 3 m) and satellite remotely
sensed data (Landsat 5TM, spatial resolution 30 m) and measures taken at ground (PAI), was deployed in the
Presidential Estate at Castelporziano (Rome, Italy). The spectral signatures of the main vegetational types of the
Estate were examined and the PAI were related to NDVI values, calculated by means of satellite and airborne
images. The adopted approach enabled PAI maps to be produced. The linear relation between measured PAI and
estimated PAI showed a higher coefficient of determination when the MIVIS data were used. The sensor high
spectral resolution has moreover allowed to better describe the structural characteristics of the main plant typologies
at Castelporziano Estate
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