83 research outputs found
Survival of periodicity in presence of incoherence in asymmetric Aharonov-Bohm rings
Magneto conductance oscillations periodic in flux with periodicity
and are seen in asymmetric Aharonov-Bohm rings as a function of
density of electrons or Fermi wave vector. Dephasing of these oscillations is
incorporated using a simple approach of wave attenuation. In this work we study
how the excitation of the oscillations and the accompanying phase
change of are affected by dephasing. Our results show that the
oscillations survive incoherence, i.e., dephasing, albeit with
reduced visibility while incoherence is also unable to obliterate the phase
change of .Comment: 4 pages, 3 figure
CURRENT MAGNIFICATION AND CIRCULATING CURRENTS IN MESOSCOPIC RINGS
We show that several novel effects related to persistent currents can arise
in open systems, which have no analogue in closed or isolated systems. We have
considered a system of a metallic ring coupled to two electron reservoirs. We
show that in the presence of a transport current, persistent currents can flow
in a ring even in the absence of magnetic field. This is related to the current
magnification effect in the ring. In the presence of magnetic field we show
that the amplitude of persistent currents is sensitive to the direction of
current flow from one reservoir to another. Finally we briefly discuss the
persistent currents arising due to two nonclassical effects namely,
Aharonov-Bohm effect and quantum tunneling.Comment: On the basis of talk given by A. M. Jayannavar at "International
Workshop on Novel Physics in Low Dimensional Systems" in Madras(India). Four
figures available on reques
Hartman effect in presence of Aharanov Bohm flux
The Hartman effect for the tunneling particle implies the independence of
group delay time on the opaque barrier width, with superluminal velocities as a
consequence. This effect is further examined on a quantum ring geometry in the
presence of Aharonov-Bohm flux. We show that while tunneling through an opaque
barrier the group delay time for given incident energy becomes independent of
the barrier thickness as well as the magnitude of the flux. The Hartman effect
is thereby extended beyond one dimension and in the presence of Aharonov-Bohm
flux.Comment: 4 pages, 4 figure
Magneto-transport in periodic and quasiperiodic arrays of mesoscopic rings
We study theoretically the transmission properties of serially connected
mesoscopic rings threaded by a magnetic flux. Within a tight-binding formalism
we derive exact analytical results for the transmission through periodic and
quasiperiodic Fibonacci arrays of rings of two different sizes. The role played
by the number of scatterers in each arm of the ring is analyzed in some detail.
The behavior of the transmission coefficient at a particular value of the
energy of the incident electron is studied as a function of the magnetic flux
(and vice versa) for both the periodic and quasiperiodic arrays of rings having
different number of atoms in the arms. We find interesting resonance properties
at specific values of the flux, as well as a power-law decay in the
transmission coefficient as the number of rings increases, when the magnetic
field is switched off. For the quasiperiodic Fibonacci sequence we discuss
various features of the transmission characteristics as functions of energy and
flux, including one special case where, at a special value of the energy and in
the absence of any magnetic field, the transmittivity changes periodically as a
function of the system size.Comment: 9 pages with 7 .eps figures included, submitted to PR
Clastic Polygonal Networks Around Lyot Crater, Mars: Possible Formation Mechanisms From Morphometric Analysis
Polygonal networks of patterned ground are a common feature in cold-climate environments. They can form through the thermal contraction of ice-cemented sediment (i.e. formed from fractures), or the freezing and thawing of ground ice (i.e. formed by patterns of clasts, or ground deformation). The characteristics of these landforms provide information about environmental conditions. Analogous polygonal forms have been observed on Mars leading to inferences about environmental conditions. We have identified clastic polygonal features located around Lyot crater, Mars (50°N, 30°E). These polygons are unusually large (> 100 m diameter) compared to terrestrial clastic polygons, and contain very large clasts, some of which are up to 15 metres in diameter. The polygons are distributed in a wide arc around the eastern side of Lyot crater, at a consistent distance from the crater rim. Using high-resolution imaging data, we digitised these features to extract morphological information. These data are compared to existing terrestrial and Martian polygon data to look for similarities and differences and to inform hypotheses concerning possible formation mechanisms. Our results show the clastic polygons do not have any morphometric features that indicate they are similar to terrestrial sorted, clastic polygons formed by freeze-thaw processes. They are too large, do not show the expected variation in form with slope, and have clasts that do not scale in size with polygon diameter. However, the clastic networks are similar in network morphology to thermal contraction cracks, and there is a potential direct Martian analogue in a sub-type of thermal contraction polygons located in Utopia Planitia. Based upon our observations, we reject the hypothesis that polygons located around Lyot formed as freeze-thaw polygons and instead an alternative mechanism is put forward: they result from the infilling of earlier thermal contraction cracks by wind-blown material, which then became compressed and/or cemented resulting in a resistant fill. Erosion then leads to preservation of these polygons in positive relief, while later weathering results in the fracturing of the fill material to form angular clasts. These results suggest that there was an extensive area of ice-rich terrain, the extent of which is linked to ejecta from Lyot crater
Near-field dispersion of produced formation water (PFW) in the Adriatic Sea: An integrated numerical–chemical approach
Data from a pre-publication independent replication initiative examining ten moral judgement effects
We present the data from a crowdsourced project seeking to replicate findings in independent laboratories before (rather than after) they are published. In this Pre-Publication Independent Replication (PPIR) initiative, 25 research groups attempted to replicate 10 moral judgment effects from a single laboratory's research pipeline of unpublished findings. The 10 effects were investigated using online/lab surveys containing psychological manipulations (vignettes) followed by questionnaires. Results revealed a mix of reliable, unreliable, and culturally moderated findings. Unlike any previous replication project, this dataset includes the data from not only the replications but also from the original studies, creating a unique corpus that researchers can use to better understand reproducibility and irreproducibility in science
The pipeline project: Pre-publication independent replications of a single laboratory's research pipeline
This crowdsourced project introduces a collaborative approach to improving the reproducibility of scientific research, in which findings are replicated in qualified independent laboratories before (rather than after) they are published. Our goal is to establish a non-adversarial replication process with highly informative final results. To illustrate the Pre-Publication Independent Replication (PPIR) approach, 25 research groups conducted replications of all ten moral judgment effects which the last author and his collaborators had “in the pipeline” as of August 2014. Six findings replicated according to all replication criteria, one finding replicated but with a significantly smaller effect size than the original, one finding replicated consistently in the original culture but not outside of it, and two findings failed to find support. In total, 40% of the original findings failed at least one major replication criterion. Potential ways to implement and incentivize pre-publication independent replication on a large scale are discussed
Galls of Cecidoses eremita Curtis and Eucecidoses minutanus Brèthes (Lepidoptera: Cecidosidae) in Magdalena, Buenos Aires Province: preliminary study and associated fauna
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