2,965 research outputs found
Estimating Spatial Econometrics Models with Integrated Nested Laplace Approximation
Integrated Nested Laplace Approximation provides a fast and effective method
for marginal inference on Bayesian hierarchical models. This methodology has
been implemented in the R-INLA package which permits INLA to be used from
within R statistical software. Although INLA is implemented as a general
methodology, its use in practice is limited to the models implemented in the
R-INLA package.
Spatial autoregressive models are widely used in spatial econometrics but
have until now been missing from the R-INLA package. In this paper, we describe
the implementation and application of a new class of latent models in INLA made
available through R-INLA. This new latent class implements a standard spatial
lag model, which is widely used and that can be used to build more complex
models in spatial econometrics.
The implementation of this latent model in R-INLA also means that all the
other features of INLA can be used for model fitting, model selection and
inference in spatial econometrics, as will be shown in this paper. Finally, we
will illustrate the use of this new latent model and its applications with two
datasets based on Gaussian and binary outcomes
Estimating Relevant Portion of Stability Region using Lyapunov Approach and Sum of Squares
Traditional Lyapunov based transient stability assessment approaches focus on
identifying the stability region (SR) of the equilibrium point under study.
When trying to estimate this region using Lyapunov functions, the shape of the
final estimate is often limited by the degree of the function chosen, a
limitation that results in conservativeness in the estimate of the SR. More
conservative the estimate is in a particular region of state space, smaller is
the estimate of the critical clearing time for disturbances that drive the
system towards that region. In order to reduce this conservativeness, we
propose a methodology that uses the disturbance trajectory data to skew the
shape of the final Lyapunov based SR estimate. We exploit the advances made in
the theory of sum of squares decomposition to algorithmically estimate this
region. The effectiveness of this technique is demonstrated on a power systems
classical model.Comment: Under review as a conference paper at IEEE PESGM 201
Le comunità di fillominatori e parassitoidi della Riserva Naturale “Bosco d’Alcamo” (Sicilia)
È stata studiata la comunità di fillominatori e parassitoidi su 16 specie di piante spontanee della Riserva Naturale “Bosco d’Alcamo”. Sono state rinvenute 17 specie di Lepidoptera e 7 specie di Diptera. Da queste sono sfarfallate circa 20 specie di parassitoidi, perlopiù rappresentate da Eulophidae e Braconidae. Viene confermata la presenza in Sicilia del Gracillariidae Phyllonorycter trifasciella Haworth e dell’Eulophidae Derostenus gemmeus Westwood. Per la prima volta Sympiesis notata (Zetterstedt) e Cirrospilus viticola (Rondani) sono stati rinvenuti come parassitoidi di Emme- tia marginea (Haworth). Inoltre S. notata è stata rinvenuta anche come parassitoide di P. trifasciella. Nel complesso viene confermato il ruolo importante dei boschi naturali, soprattutto querceti, come riserva di entomofauna e di diversità biologica.Leafminer and parasitoid community of the Nature Reserve “Bosco d’Alcamo” (Sicily). The leafminer and parasitoid communities of the Nature Reserve “Bosco D’Alcamo” was studied on 16 spontaneous plants. 17 Lepidoptera and 7 Diptera species were detected. About 20 parasitoid species emerged mainly represented by Eulophidae and Braconidae. The presence in Sicily of the Gracillariidae Phyllonorycter trifasciella Haworth was confirmed, as well as that of Eulophidae Derostenus gemmeus Westwood. Sympiesis notata (Zetterstedt) and Cirrospilus viticola (Rondani) were recorded for the first time as parasitoid of Emmetia marginea (Haworth). S. notata was record- ed also as a new parasitoid of P. trifasciella. The important role of natural woods, especially oaks, as reservoir of entomofauna and biodiversity was confirmed
Bayesian model averaging with the integrated nested Laplace approximation
The integrated nested Laplace approximation (INLA) for Bayesian inference is
an efficient approach to estimate the posterior marginal distributions of the
parameters and latent effects of Bayesian hierarchical models that can be
expressed as latent Gaussian Markov random fields (GMRF). The representation as
a GMRF allows the associated software R-INLA to estimate the posterior
marginals in a fraction of the time as typical Markov chain Monte Carlo
algorithms. INLA can be extended by means of Bayesian model averaging (BMA) to
increase the number of models that it can fit to conditional latent GMRF. In
this paper we review the use of BMA with INLA and propose a new example on
spatial econometrics models.Comment: Submitted to Econometrics (MDPI
Spin-dependent direct gap emission in tensile-strained Ge films on Si substrates
The circular polarization of direct gap emission of Ge is studied in
optically-excited tensile-strained Ge-on-Si heterostructures as a function of
doping and temperature. Owing to the spin-dependent optical selection rules,
the radiative recombinations involving strain-split light (cG-LH) and heavy
hole (cG-HH) bands are unambiguously resolved. The fundamental cG-LH transition
is found to have a low temperature circular polarization degree of about 85%
despite an off-resonance excitation of more than 300 meV. By photoluminescence
(PL) measurements and tight binding calculations we show that this
exceptionally high value is due to the peculiar energy dependence of the
optically-induced electron spin population. Finally, our observation of the
direct gap doublet clarifies that the light hole contribution, previously
considered to be negligible, can dominate the room temperature PL even at low
tensile strain values of about 0.2%
Surgical Versus Medical Treatment for Diabetic Macular Edema: A Review
We aimed to compare the results of pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling, an alternative therapeutic strategy, with those of medical treatment for chronic macular edema. We conducted a review of the literature on the microscopic, anatomical, and functional reasons for performing PPV with ILM peeling in patients with diabetic macular edema (DME). We searched the PubMed database for articles published between 2000 and 2017. We used the medical subject heading “vitrectomy diabetic macular edema†and the keywords “diabetic macular edemaâ€, “internal limiting membrane peelingâ€, “pars plana vitrectomyâ€, “diabetic retinopathyâ€, and “optical coherence tomographyâ€. Analysis of the literature revealed that cytokines, vascular endothelial growth factor, reactive oxygen species (ROS), and advanced glycation end-products (AGEs) play a unique role in DME. The vitreous cavity serves as a physiological reservoir for all inflammatory molecules. AGE receptors are localized at the footplates of Müller cells and the external limiting membrane (ELM). The footplates of Müller cells are in contact with the ILM, which suggests that they might be responsible for the structural damage (i.e., thickening) observed in the ILM of patients with DME. Therefore, PPV could allow a reduction of cytokines and pro-inflammatory molecules from the vitreous cavity. ILM peeling could eliminate not only the physical traction of a thickened structure, but also the natural reservoir of AGEs, ROS, and inflammatory molecules. PPV with ILM peeling is a surgical option that should be considered when treating patients with chronic DME
Diagnostic value of transvaginal 'tenderness-guided' ultrasonography for the prediction of location of deep endometriosis
BACKGROUND: The aim was to evaluate the diagnostic accuracy of transvaginal tenderness-guided ultrasonography in the identification of location of deep endometriosis. METHODS: Consecutive women scheduled for surgery in our Department for clinically suspected endometriosis were included in this prospective study. All women underwent modified transvaginal ultrasonography using a stand-off in the week before surgery, which also evaluated the painful sites evocated by a gentle pressure of the probe. Five locations of deep endometriosis were considered: vaginal walls, rectovaginal septum, rectosigmoid involvement, uterosacral ligaments and anterior compartment (anterior pouch and/or bladder). Sensitivity, specificity and likelihood ratios (LR1/2) were calculated with 95% confidence intervals (CIs). RESULTS: We included 88 women; surgery associated with histopathological evaluation revealed deep endometriosis in different pelvic locations in 72 patients. With respect to the vaginal walls, transvaginal ultrasonography had a sensitivity of 91% (95% CI, 79 –97%), specificity of 89% (95% CI, 81–93%), an LR1 of 8.2 and an LR2 of 0.09. For endometriosis of rectovaginal septum, transvaginal ultrasonography had a sensitivity of 74% (95% CI, 64–80%), specificity of 88% (95% CI, 4–8%), an LR1 of 6.2 and an LR2 of 0.3. For other locations, the sensitivity was lower (ranging from 67% to 33%) with a comparable specificity. CONCLUSIONS: This technique shows a high specificity and sensitivity in the detection of vaginal and rectovaginal endometriosis. Good specificity associated with a lower sensitivity was obtained in the diagnosis of deep endometriosis of uterosacral ligaments, rectosigmoid involvement or anterior deep endometriosis
Quantum point contact conductance in NINS junctions
The effect of an insulating barrier located at a distance from a NS
quantum point contact is analyzed in this work. The Bogoliubov de Gennes
equations are solved for NINS junctions (S: anysotropic superconductor, I:
insulator and N: normal metal), where the NIN region is a quantum wire. For , bound states and resonances in the differential conductance are
predicted. These resonances depend on the symmetry of the pair potential, the
strength of the insulating barrier and . Our results show that in a NINS
quantum point contact the number of resonances vary with the symmetry of the
order parameter. This is to be contrasted with the results for the NINS
junction, in which only the position of the resonances changes with the
symmetry.Comment: 5 pages, 5 Figures, RevTex
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