3,836 research outputs found
Twisted Mahler discrete residues
Recently we constructed Mahler discrete residues for rational functions and
showed they comprise a complete obstruction to the Mahler summability problem
of deciding whether a given rational function is of the form
for some rational function and an integer . Here we
develop a notion of -twisted Mahler discrete residues for
, and show that they similarly comprise a complete
obstruction to the twisted Mahler summability problem of deciding whether a
given rational function is of the form for some
rational function and an integer . We provide some initial
applications of twisted Mahler discrete residues to differential creative
telescoping problems for Mahler functions and to the differential Galois theory
of linear Mahler equations
Defective transport properties of three-terminal carbon nanotube junctions
We investigate the transport properties of three terminal carbon based
nanojunctions within the scattering matrix approach. The stability of such
junctions is subordinated to the presence of nonhexagonal arrangements in the
molecular network. Such "defective" arrangements do influence the resulting
quantum transport observables, as a consequence of the possibility of acting as
pinning centers of the correspondent wavefunction. By investigating a fairly
wide class of junctions we have found regular mutual dependencies between such
localized states at the carbon network and a strikingly behavior of the
conductance. In particular, we have shown that Fano resonances emerge as a
natural result of the interference between defective states and the extended
continuum background. As a consequence, the currents through the junctions
hitting these resonant states might experience variations on a relevant scale
with current modulations of up to 75%.Comment: 8 pages, 8 figure
Estabilidad de varios tipos de comunidad en ecosistemas de dunas en el noreste de China
The stability of artificial, sand-binding communities has not yet fully studied. A
similarity index was developed to evaluate the stability of artificial communities in
shifting and semi-fixed sand dunes. This similarity index consisted of 8 indicators (i.e.,
vegetation cover, Shannon-Wiener Index, biomass, organic matter, Total N, available P
and K, and sand particle ratio). The relative weight of these indicators was obtained
using an analytic hierarchy process (AHP) method. Stability was compared on
Artemisia halodendron Turczaninow ex Besser, Bull communities in shifting and semifixed
sand dunes, and of Caragana microphylla Lam. communities with different planting
ages. The similarity indexes of the A. halodendron communities were 0.24 and 0.54 in
shifting and semi-fixed sand dunes, respectively. The peak stability of C. microphylla
communities was 0.55, and it was reached when these communities were 20-year-old.
It is suggested that A. halodendron communities should be planted preferentially in
semi-fixed to moving sand dunes. Furthermore, the planting age of artificial communities
should be included in planting programs. This study improved the understanding
of some mechanisms contributing to maintain community stability, and is critical for
guiding the artificial planting in sand dunes.La estabilidad de comunidades artificiales que contribuyen a la fijación de suelos
arenosos no se ha estudiado completamente. Se desarrolló un Ãndice de similitud para
evaluar la estabilidad de comunidades artificiales en dunas móviles y fijadas medianamente.
Este Ãndice de similitud consistió de 8 indicadores (cobertura vegetal, Ãndice
de Shannon-Wiener, biomasa, materia orgánica, N total, P y K disponibles, y relación
de partÃculas de arena). La importancia relativa de estos indicadores se obtuvo utilizando
un método de procesamiento jerárquico analÃtico (AHP). Se comparó la estabilidad
de comunidades de Artemisia halodendron Turczaninow ex Besser, Bull en dunas
móviles y fijadas medianamente, y la de comunidades de Caragana microphylla Lam.
de diferentes edades de plantación. Los Ãndices de similitud de las comunidades de
A. halodendron fueron 0,24 y 0,54 en dunas móviles y fijadas medianamente, respectivamente.
La estabilidad máxima de las comunidades de C. microphylla fue 0,55, la que
se obtuvo cuando dichas comunidades alcanzaron 20 años de edad. Se sugiere que las
comunidades de A. halodendron se deberÃan plantar preferencialmente en dunas fijadas
medianamente a móviles. Además, la edad de plantación de las comunidades artificiales
se deberÃa incluir en programas de plantación. Este estudio mejoró el entendimiento de
algunos mecanismos que contribuyen a mantener la estabilidad de las comunidades, y
es crÃtico para guiar la plantación artificial en áreas de dunas.Fil: Tang, Yi.Fil: Li, Xiaolan.Fil: Wu, Jinhua.Fil: Busso, Carlos Alberto
Enhanced discrimination of DNA molecules in nanofluidic channels through multiple measurements
Author Manuscript 2013 March 21.Nanofluidic sensing elements have been the focus of recent experiments for numerous applications ranging from nucleic acid fragment sizing to single-molecule DNA sequencing. These applications critically rely on high measurement fidelity, and methods to increase resolution are required. Herein, we describe fabrication and testing of a nanochannel device that enhances measurement resolution by performing multiple measurements (>100) on single DNA molecules. The enhanced measurement resolution enabled length discrimination between a mixture of λ-DNA (48.5 kbp) and T7 DNA (39.9 kbp) molecules, which were detected as transient current changes during translocation of the molecules through the nanochannel. As long DNA molecules are difficult to resolve quickly and with high fidelity with conventional electrophoresis, this approach may yield potentially portable, direct electrical sizing of DNA fragments with high sensitivity and resolution.National Institutes of Health (U.S.) (Grant R21EB009180)United States. Air Force (Contract FA8721-05-C- 0002
Measuring valley polarization in two-dimensional materials with second-harmonic spectroscopy
A population imbalance at different valleys of an electronic system lowers
its effective rotational symmetry. We introduce a technique to measure such
imbalance - a valley polarization - that exploits the unique fingerprints of
this symmetry reduction in the polarization-dependent second-harmonic
generation (SHG). We present the principle and detection scheme in the context
of hexagonal two-dimensional crystals, which include graphene-based systems and
the family of transition metal dichalcogenides, and provide a direct
experimental demonstration using a 2H-MoSe monolayer at room temperature.
We deliberately use the simplest possible setup, where a single pulsed laser
beam simultaneously controls the valley imbalance and tracks the SHG process.
We further developed a model of the transient population dynamics which
analytically describes the valley-induced SHG rotation in very good agreement
with the experiment. In addition to providing the first experimental
demonstration of the effect, this work establishes a conceptually simple,
com-pact and transferable way of measuring instantaneous valley polarization,
with direct applicability in the nascent field of valleytronics
A use error taxonomy for improving human-machine interface design in medical devices
Use error is one of the leading causes of medical device incidents. It is crucial for all stakeholders to have a unified means to better understand, classify, communicate, and prevent/avoid medical device use errors. In this paper, we present our ongoing work on developing a new use error taxonomy for medical devices that has the potential to enable fine-grained analysis of use errors and their root causes in system design. Our ultimate goal is to create a generic framework that can be used by medical device designers to better identify effective design solutions to mitigating use errors.Paolo Masci is funded by the ERDF (European Regional De-velopment Fund) through the Operational Programme for Compet-itiveness and Internationalisation – COMPETE 2020 Programmewithin the project POCI-01-0145-FEDER-006961, and by NationalFunds through the Portuguese funding agency FCT (Fundação paraa Ciência e a Tecnologia) as part of project UID/EEA/50014/2013. José C. Campos is funded by project NanoSTIMA: Macro-to-NanoHuman Sensing: Towards Integrated Multimodal Health Monitor-ing and Analytics/NORTE-01-0145-FEDER-000016, financed bythe North Portugal Regional Operational Programme NORTE 2020,under the PORTUGAL 2020 Partnership Agreement, and through the European Regional Development Fund (ERDF)
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