833 research outputs found
SYM, Chern-Simons, Wess-Zumino Couplings and their higher derivative corrections in IIA Superstring theory
We find the entire form of the amplitude of two fermion strings (with
different chirality), a massless scalar field and one closed string
Ramond-Ramond (RR) in IIA superstring theory which is different from its IIB
one. We make use of a very particular gauge fixing and explore several new
couplings in IIA. All infinite - channel scalar poles and - channel
fermion poles are also constructed. We find new form of higher derivative
corrections to two fermion two scalar couplings and show that the first simple
channel scalar pole for case can be obtained by having new
higher derivative corrections to SYM couplings at third order of . We
find that the general structure and the coefficients of higher derivative
corrections to two fermion two scalar couplings are completely different from
the derived higher derivative corrections of type IIB.Comment: 29 pages, no figure,Latex file,published version in EPJ
On higher derivative corrections to Wess-Zumino and Tachyonic actions in type II super string theory
We evaluate in detail the string scattering amplitude to compute different
interactions of two massless scalars, one tachyon and one closed string
Ramond-Ramond field in type II super string theory. In particular we find two
scalar field and two tachyon couplings to all orders of up to
on-shell ambiguity. We then obtain the momentum expansion of this amplitude and
apply this infinite number of couplings to actually check that the infinite
number of tachyon poles of S-matrix element of this amplitude for the
case (where is the spatial dimension of a D-brane and is the rank
of a Ramond-Ramond field strength) to all orders of is precisely
equal to the infinite number of tachyon poles of the field theory. In addition
to confirming the couplings of closed string Ramond-Ramond field to the
world-volume gauge field and scalar fields including commutators, we also
propose an extension of the Wess-Zumino action which naturally reproduces these
new couplings in field theory such that they could be confirmed with direct
S-matrix computations. Finally we show that the infinite number of massless
poles and contact terms of this amplitude for the case can be
reproduced by Chern-Simons, higher derivative corrections of the Wess-Zumino
and symmetrized trace tachyon DBI actions.Comment: 51 pages, some refs and comments added, typos are removed. Almost all
ambiguities in BPS and non-BPS effective actions have been addresse
Explicit physics-informed neural networks for non-linear upscaling closure: the case of transport in tissues
In this work, we use a combination of formal upscaling and data-driven
machine learning for explicitly closing a nonlinear transport and reaction
process in a multiscale tissue. The classical effectiveness factor model is
used to formulate the macroscale reaction kinetics. We train a multilayer
perceptron network using training data generated by direct numerical
simulations over microscale examples. Once trained, the network is used for
numerically solving the upscaled (coarse-grained) differential equation
describing mass transport and reaction in two example tissues. The network is
described as being explicit in the sense that the network is trained using
macroscale concentrations and gradients of concentration as components of the
feature space.
Network training and solutions to the macroscale transport equations were
computed for two different tissues. The two tissue types (brain and liver)
exhibit markedly different geometrical complexity and spatial scale (cell size
and sample size). The upscaled solutions for the average concentration are
compared with numerical solutions derived from the microscale concentration
fields by a posteriori averaging. There are two outcomes of this work of
particular note: 1) we find that the trained network exhibits good
generalizability, and it is able to predict the effectiveness factor with high
fidelity for realistically-structured tissues despite the significantly
different scale and geometry of the two example tissue types; and 2) the
approach results in an upscaled PDE with an effectiveness factor that is
predicted (implicitly) via the trained neural network. This latter result
emphasizes our purposeful connection between conventional averaging methods
with the use of machine learning for closure; this contrasts with some machine
learning methods for upscaling where the exact form of the macroscale equation
remains unknown
Hybrid(Luminescent and Fresnel ) Concentrators to Improve Solar Panel Conversion Efficiency
The spectral response of the Si solar cell does not coincidence with the sun irradiance spectrum, so the efficiency of the Si solar cell is not high. To improve the Si solar cell one try to make use of most region of the sun spectrum by using dyes which absorb un useful wavelengths and radiate at useful region of spectrum (by stock shift). Fluorescence's dye is used as luminescent concentrator to increase the efficiency of the solar cell. The results show that the performance efficiency and out power for crystalline silicon solar cells are improved
Stability and photo-thermal conversion performance of binary nanofluids for solar absorption refrigeration systems
The photo-thermal conversion characteristics of a long-term stable binary nanofluid (nanoparticles in 50 wt% lithium bromide-50 wt% water) were investigated in this work. The stability of the binary nanofluid against the agglomeration and sedimentation process was evaluated by a high-speed centrifuge analyzer and transmission electron microscopy. The photo thermal conversion efficiency of the nanofluid was also studied using a solar simulator. Experimental results indicated that the use of the binary nanofluid could significantly increase the light trapping efficiency and, therefore, the bulk temperature, which in turn could increase the evaporation rate due to surface localized heat generation. The experimental results showed the increase of 4.2 and 4.9 percent solar radiative energy in the form of sensible heat after addition of 64 and 321 mg/l iron oxide NPs to the pure water, respectively. The increasing percent is 4.9% and 11.9% for latent heat efficiency in the presence of 64 and 321 mg/l iron oxide NPs, respectively. Possessing both high stability and excellent photo-thermal conversion rate, rod shape iron oxide nanoparticles is suggested to be a potential candidate used for the solar absorption refrigeration systems
Radiosurgery for the control of glomus jugulare tumours
Objective: To ascertain the efficacy of stereotactic radiosurgery (gamma knife) for the control of glomus jugulare tumours.Method: Between March 1994 and December 1997 we treated eight patients of glomus jugulare tumour with radiosurgery. These patients have been followed for more than four years (range 52 to 97 months). The age of the patients ranged between 32-64 years (mean 53 years). The male: female ratio was 3:5. Three patients had previously undergone surgery and one had unsuccessful embolization. The dose applied to tumour margin ranged between 16-25 Gy (median 25 Gy). Patients were followed up with yearly MRI scans and where possible with cerebral angiography.Results: All patients showed stabilisation of their symptoms following radiosurgery and six improved clinically. Five of these patients showed decrease in the size of lesion seen objectively on radiology, either slight to moderate decrease seen on the MRI scan or reduction in size and vascularity seen on cerebral angiography. The procedure is minimally invasive and none of the patients showed any adverse effect to radiosurgery.Conclusion: These results are encouraging but because of its naturally slow growth rate, up to 10 years of follow up will be necessary to establish a cure rate after radiosurgery for these lesions
Finite temperature Casimir effect in the presence of nonlinear dielectrics
Starting from a Lagrangian, electromagnetic field in the presence of a
nonlinear dielectric medium is quantized using path-integral techniques and
correlation functions of different fields are calculated. The susceptibilities
of the nonlinear medium are obtained and their relation to coupling functions
are determined. Finally, the Casimir energy and force in the presence of a
nonlinear medium at finite temperature is calculated.Comment: 16 pages, 0 figure
Image fusion using multivariate and multidimensional EMD.
We present a novel methodology for the fusion of multiple (two or more) images using the multivariate extension of empirical mode decomposition (MEMD). Empirical mode decomposition (EMD) is a data-driven method which decomposes input data into its intrinsic oscillatory modes, known as intrinsic mode functions (IMFs), without making a priori assumptions regarding the data. We show that the multivariate and multidimensional extensions of EMD are suitable for image fusion purposes. We further demonstrate that while multidimensional extensions, by design, may seem more appropriate for tasks related to image processing, the proposed multivariate extension outperforms these in image fusion applications owing to its mode-alignment property for IMFs. Case studies involving multi-focus image fusion and pan-sharpening of multi-spectral images are presented to demonstrate the effectiveness of the proposed method
Finite temperature Cherenkov radiation in the presence of a magnetodielectric medium
A canonical approach to Cherenkov radiation in the presence of a
magnetodielectric medium is presented in classical, nonrelativistic and
relativistic quantum regimes. The equations of motion for the canonical
variables are solved explicitly for both positive and negative times. Maxwell
and related constitute equations are obtained. In the large-time limit, the
vector potential operator is found and expressed in terms of the medium
operators. The energy loss of a charged particle, emitted in the form of
radiation, in finite temperature is calculated. A Dirac equation concerning the
relativistic motion of the particle in presence of the magnetodielectric medium
is derived and the relativistic Cherenkov radiation at zero and finite
temperature is investigated. Finally, it is shown that the Cherenkov radiation
in nonrelativistic and relativistic quantum regimes, unlike its classical
counterpart, introduces automatically a cutoff for higher frequencies beyond
which the power of radiation emission is zero.Comment: To be appear in PR
Chromophobe renal cell carcinoma mimicking cortical invasion by synchronous invasive urothelial carcinoma of the intra-renal collecting system on CT urography
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