2,108 research outputs found
Modelling background charge rearrangements near single-electron transistors as a Poisson process
Background charge rearrangements in metallic single-electron transistors are
modelled in two-level tunnelling systems as a Poisson process with a scale
parameter as only variable. The model explains the recent observation of
asymmetric Coulomb blockade peak spacing distributions in metallic
single-electron transistors. From the scale parameter we estimate the average
size of the tunnelling systems, their density of states, and the height of
their energy barrier. We conclude that the observed background charge
rearrangements predominantly take place in the substrate of the single-electron
transistor.Comment: 7 pages, 2 eps figures, used epl.cls macro include
Non-critical string pentagon equations and their solutions
We derive pentagon type relations for the 3-point boundary tachyon
correlation functions in the non-critical open string theory with generic
c_{matter} < 1 and study their solutions in the case of FZZ branes. A new
general formula for the Liouville 3-point factor is derived.Comment: 18 pages, harvmac; misprints corrected, section 3.2 extended, a new
general formula for the Liouville 3-point factor adde
Texturizzazione laser della lega di magnesio AZ31 per migliorare l’adesione nelle applicazioni biomedicali
"Laser surface texturing of AZ31 Magnesium Alloy
to improve adhesion in biomedical application
Cardiovascular stent have assumed a primary role to solve
heart problems related to constraints that lead to the
malfunctioning of a hollow organ. The research is shifting
more and more towards the creations of less invasive stent
having biocompatibility and biodegradability as primary
requirements. Metal that best meets both these
requirements and also the structural ones is Magnesium
and its alloys. The greatest limit to the use of this material
comes from its low corrosion resistance that it is
manifested at the body pH. The idea at the basis of this work
is to cover the Magnesium stent with a biodegradable
polymer to increase its resistance to corrosion. The
following paper focuses the study on the texturing
surface treatments, achievable by a laser beam, in order to
optimize the adhesion between the substrate and the
polymer. The Magnesium alloy used is AZ31. Studies of
surface modification through the mechanisms of the
remelting and microdrilling by laser have been performed
on the AZ31 surface. The characterization of the selected
surfaces in terms of roughness variations, changes in
wettability, oxides formation and geometry of the obtained
structures, led to the identification of a limited number of
conditions that will be further investigated.
Higher-Dimensional Twistor Transforms using Pure Spinors
Hughston has shown that projective pure spinors can be used to construct
massless solutions in higher dimensions, generalizing the four-dimensional
twistor transform of Penrose. In any even (Euclidean) dimension d=2n,
projective pure spinors parameterize the coset space SO(2n)/U(n), which is the
space of all complex structures on R^{2n}. For d=4 and d=6, these spaces are
CP^1 and CP^3, and the appropriate twistor transforms can easily be
constructed. In this paper, we show how to construct the twistor transform for
d>6 when the pure spinor satisfies nonlinear constraints, and present explicit
formulas for solutions of the massless field equations.Comment: 17 pages harvmac tex. Modified title, abstract, introduction and
references to acknowledge earlier papers by Hughston and other
Singular vectors by Fusions in affine su(2)
Explicit expressions for the singular vectors in the highest weight
representations of are obtained using the fusion formalism of
conformal field theory.Comment: 7 page
Estimativa dos valores de saldo de radiação e fluxo de calor no solo em diferentes condições antrópicas na bacia do rio Ji-Paraná, Rondônia.
Use change and land cover has significant influence on energy flows. Thus, this study aimed to compare the net radiation and soil heat flux on two dates, 19/07/1984 and 25/06/2010 from a locality of river basin Ji-Paraná, Rondônia. To develop the study, an algorithm Surface Energy Balance Algorithm for Land (SEBAL) allowing the estimation of energy flows according to the cover. The model was applied in the study area in a sequence of steps, where the outcome of interest was the net radiation at the surface and the flow of heat in the soil. The results show that on average the net radiation was greater in the scene where the predominant areas of forest, 19/07/1984, since the albedo of the vegetation is lower than in surface of bare ground or with less dense vegetation as observed in the scene 25/06/2010. The values of soil heat flux are larger at the scene of 25/06/2010 and occupy a larger surface due to human action. This shows that the replacement of forest for agriculture, grazing and urbanization are causing decrease the net radiation and increase the flow of heat in the soil, thereby increasing the emission of long wave radiation that affect the surface temperature, air temperature and the hydrological cycle
Quantum matrix algebra for the SU(n) WZNW model
The zero modes of the chiral SU(n) WZNW model give rise to an intertwining
quantum matrix algebra A generated by an n x n matrix a=(a^i_\alpha) (with
noncommuting entries) and by rational functions of n commuting elements
q^{p_i}. We study a generalization of the Fock space (F) representation of A
for generic q (q not a root of unity) and demonstrate that it gives rise to a
model of the quantum universal enveloping algebra U_q(sl_n), each irreducible
representation entering F with multiplicity 1. For an integer level k the
complex parameter q is an even root of unity, q^h=-1 (h=k+n) and the algebra A
has an ideal I_h such that the factor algebra A_h = A/I_h is finite
dimensional.Comment: 48 pages, LaTeX, uses amsfonts; final version to appear in J. Phys.
Emission from Water Vapor and Absorption from Other Gases at 5-7.5 Microns in Spitzer-IRS Spectra of Protoplanetary Disks
We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming
region showing emission in Spitzer Space Telescope Infrared Spectrograph (IRS)
5-7.5 micron spectra from water vapor and absorption from other gases in these
stars' protoplanetary disks. Seven stars' spectra show an emission feature at
6.6 microns due to the nu_2 = 1-0 bending mode of water vapor, with the shape
of the spectrum suggesting water vapor temperatures > 500 K, though some of
these spectra also show indications of an absorption band, likely from another
molecule. This water vapor emission contrasts with the absorption from warm
water vapor seen in the spectrum of the FU Orionis star V1057 Cyg. The other
six of the thirteen stars have spectra showing a strong absorption band,
peaking in strength at 5.6-5.7 microns, which for some is consistent with
gaseous formaldehyde (H2CO) and for others is consistent with gaseous formic
acid (HCOOH). There are indications that some of these six stars may also have
weak water vapor emission. Modeling of these stars' spectra suggests these
gases are present in the inner few AU of their host disks, consistent with
recent studies of infrared spectra showing gas in protoplanetary disks.Comment: 33 pages, 9 figures, to appear in the 20 August, 2014, V791 - 2 issue
of the Astrophysical Journa
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