6,580 research outputs found
Near-Field Directionality Beyond the Dipole Approximation: Electric Quadrupole and Higher-Order Multipole Angular Spectra
Within the context of spin-related optical phenomena, the near-field
directionality is generally understood from the quantum spin Hall effect of
light, according to which the transverse spin of surface or guided modes is
locked to the propagation direction. So far, most previous works have been
focused on the spin properties of circularly polarized dipolar sources.
However, in near-field optics, higher-order multipole sources (e.g.,
quadrupole, octupole, and so on) might become relevant, so a more in-depth
formulation would be highly valuable. Building on the angular spectrum
representation, we provide a general, analytical, and ready-to-use treatment in
order to address the near-field directionality of any multipole field,
particularizing to the electric quadrupole case. Besides underpinning and
upgrading the current framework on spin-dependent directionality, our results
may open up new perspectives for engineering light-matter coupling at the
nanoscale.Comment: 7 pages, 2 figures. Supplemental Material (19 pages). Supplemental
tools (calculator of angular spectra and animation) available at
https://doi.org/10.5281/zenodo.267790
The Valuation of Mortgage Backed Securities with Stochastic Probabilities of Default and Prepayment
The aim of this paper is to provide a new approach to project the Mortgage Backed Securities (MBS) cash flows in emerging markets where collateral information is limited, wrong or scarce. Under this framework, we use the Cox Process to model stochastic probabilities of prepayment and default. The model deals with general intensity dynamics and is applied to the starting MBS Mexican market.Mortgage valuation, MBS prepayment, MBS default, MBS curtailment, Cox Process.
Técnicas especiales en el diagnóstico de tumores óseos
Se hace una exposición del valor actual desde el punto de vista diagnóstico y
pronóstico de las técnicas especiales aplicables a los tumores óseos por el patólogo. En histoquimia
se resalta el valor práctico de las técnicas de PAS y fosfatasa alcalina para el diagnóstico del
sarcoma de Ewing y del osteosarcoma respectivamente. Se comenta el valor de la aplicación de
la microscopía electrónica en el diagnóstico de los tumores de células redondas pequeñas (sarcoma
de Ewing, tumor neuroectodérmico periférico, linfoma primitivo óseo y metástasis de neuroblastoma
y de rabdomiosarcoma embrionario) y de los sarcomas fusocelulares (fibrosarcoma,
leiomiosarcoma embrionario) y de los sarcoma fusocelulares (fibrosarcoma, leiomiosarcoma primitivo
de hueso y sarcoma sinovial) y de la aplicación de la inmunocitoquimia en los mismos tó-
picos así como el diagnóstico diferencial del condrosarcoma, cordoma y metástasis de
carcinoma mucosecretor en columna. Se comenta que la citología sólo es válida cuando es utilizada
por un patólogo experto en patología tumoral ósea y en citopatología y que su aplicación
es muy limitada. Se hace una revisión del valor de los estudios de ploidia con las técnicas de citometría
de flujo y estática, resaltando su valor en la valoración pronóstica de ciertos tumores
(condrosarcoma; sarcoma de Ewing). Finalmente, se comenta la aplicación diagnóstica de los estudios
citogenéticos en el sarcoma de Ewing y el futuro de dichas técnicas de esta patología.In terms of diagnosis and prognosis, the present value of different sophisticated
techniques applied for the patologist on bone tumors is reviewed. Histochemically, alkaline phosphatase
and PAS techniques are both very important for the diagnosis of osteosarcoma and
Ewing's sarcoma respectively. The value of electronic microscopy and immunohistochemistry for
diagnosis of round small cells tumors (Ewing's sarcoma, neuroectodermic tumors, primary bone
lymphoma and metastatic neuroblastoma) and fusocellular sarcomas (fibrosarcoma, leiomyosarcoma
of bone and synovial sarcoma) isdiscussed. The differential diagnosis of chondrosarcoma,
chordoma and metastatic mucosecretor carcinoma at the spine by using immunohistochemistry is
reviewed. The aplication of cytology is very limited and only useful in the hands of patologist expert
in bone tumors. Recent studies on cellular ploidy using the techniques of flow and static cytometry
have shown prognostic value in certain tumors such as chondrosarcoma. The future
seem s to be cytogenetics as have been demostrated already for Ewing sarcoma
Understanding the impact of line-of-sight in the ergodic spectral efficiency of cellular networks
In this paper we investigate the impact of lineof-sight (LoS) condition in the ergodic spectral efficiency of cellular networks. To achieve this goal, we have considered the kappa-mu shadowed model, which is a general model that provides an excellent fit to a wide set of propagation conditions. To overcome the mathematical complexity of the analysis, we have split the analysis between large and small-scale effects. Building on the proposed framework, we study a number of scenarios that range from heavily-fluctuating LoS to deterministic-LoS. Finally, we shed light on the interplay between fading severity and spectral efficiency by means of the amount of fading.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Improved wear performance of ultra high molecular weight polyethylene coated with hydrogenated diamond like carbon
Hydrogenated diamond like carbon (DLCH) thin films were deposited on medical grade ultra high molecular weight polyethylene (UHMWPE) by radio frequency plasma enhanced chemical vapor deposition. The DLCH coating thicknesses ranged from 250 to 700. nm. The substrates were disks made of UHMWPEs typically used for soft components in artificial joints, namely virgin GUR 1050 and highly crosslinked (gamma irradiated in air to 100. kGy) UHMWPEs. Mechanical and tribological properties under bovine serum lubrication at body temperature were assessed on coated and uncoated polyethylenes by means of nano-hardness and ball-on-disk tests, respectively. Morphological features of the worn surfaces were obtained by confocal microscopy and scanning electron microscopy. This study confirms an increase in surface hardness and good wear resistance for coated materials after 24. h of sliding test compared to uncoated polyethylene. These results point out that to coat UHMWPE with DLCH films could be a potential method to reduce backside wear in total hip and knee arthroplasties.Ministerio de Ciencia y Educación MAT2006-12603- C02-01, CSD2008-0002
Biorefineries: Achievements and challenges for a bio-based economy
Funding
This work was supported by a project (FQM-176) financed
by the Junta de Andalucía. FM-M, acknowledges the support
from the Global Challenges Research Fund from Swansea
University, and from the Royal Society of Chemistry
Enablement Grant (E21-7051491439).Climate change, socioeconomical pressures, and new policy and legislation are
driving a decarbonization process across industries, with a critical shift from a
fossil-based economy toward a biomass-based one. This new paradigm implies
not only a gradual phasing out of fossil fuels as a source of energy but also a
move away from crude oil as a source of platform chemicals, polymers, drugs,
solvents and many other critical materials, and consumer goods that are
ubiquitous in our everyday life. If we are to achieve the United Nations’
Sustainable Development Goals, crude oil must be substituted by renewable
sources, and in this evolution, biorefineries arise as the critical alternative to
traditional refineries for producing fuels, chemical building blocks, and materials
out of non-edible biomass and biomass waste. State-of-the-art biorefineries
already produce cost-competitive chemicals and materials, but other products
remain challenging from the economic point of view, or their scaled-up
production processes are still not sufficiently developed. In particular, lignin’s
depolymerization is a required milestone for the success of integrated
biorefineries, and better catalysts and processes must be improved to
prepare bio-based aromatic simple molecules. This review summarizes
current challenges in biorefinery systems, while it suggests possible
directions and goals for sustainable development in the years to come.Project (FQM-176) financed by the Junta de AndalucíaGlobal Challenges Research Fund from Swansea UniversityRoyal Society of Chemistry Enablement Grant (E21-7051491439
Efficient transfer entropy analysis of non-stationary neural time series
Information theory allows us to investigate information processing in neural
systems in terms of information transfer, storage and modification. Especially
the measure of information transfer, transfer entropy, has seen a dramatic
surge of interest in neuroscience. Estimating transfer entropy from two
processes requires the observation of multiple realizations of these processes
to estimate associated probability density functions. To obtain these
observations, available estimators assume stationarity of processes to allow
pooling of observations over time. This assumption however, is a major obstacle
to the application of these estimators in neuroscience as observed processes
are often non-stationary. As a solution, Gomez-Herrero and colleagues
theoretically showed that the stationarity assumption may be avoided by
estimating transfer entropy from an ensemble of realizations. Such an ensemble
is often readily available in neuroscience experiments in the form of
experimental trials. Thus, in this work we combine the ensemble method with a
recently proposed transfer entropy estimator to make transfer entropy
estimation applicable to non-stationary time series. We present an efficient
implementation of the approach that deals with the increased computational
demand of the ensemble method's practical application. In particular, we use a
massively parallel implementation for a graphics processing unit to handle the
computationally most heavy aspects of the ensemble method. We test the
performance and robustness of our implementation on data from simulated
stochastic processes and demonstrate the method's applicability to
magnetoencephalographic data. While we mainly evaluate the proposed method for
neuroscientific data, we expect it to be applicable in a variety of fields that
are concerned with the analysis of information transfer in complex biological,
social, and artificial systems.Comment: 27 pages, 7 figures, submitted to PLOS ON
Sobre la convergencia del modelo GARCH(1,1)-M al movimiento geométrico browniano con reversión a la media
This paper shows, under certain conditions, the convergence of the GARCH (1.1)-M model to the geometric Brownian motion with mean reversion (diffusion GARCH process). The importance from this result is that the problem of inference on the parameters of the valuation models of options with stochastic volatility can be reduced by estimating the model GARCH (1.1)-M. It is also carried out a discussion on the assumptions that ensure the existence and uniqueness of the limit process. Finally, it is provided a quick demonstration of the convergence, which is less formal, but more intuitive and easy to remember.Convergencia de procesos estocásticos, valuación de derivados, volatilidad estocástica
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