Performance Assessment of Different Roof Integrated Photovoltaic Modules under Mediterranean Climate

AbstractMany countries, for aesthetic purposes, offer economic advantages (tax deductions, incentives, etc..) for the installation of building integrated photovoltaic modules (BIPV), with water-tightness capability and adequate mechanical resistance in order to substitute tile covering or part of it. Nevertheless, poor or absent ventilation under BIPV panels could cause them to overheat and reduce their efficiency.It is well established that the presence of an air gap between a photovoltaic (PV) module and roof covering facilitates ventilation cooling under the device and consequently reduces cell temperature and improves its performance.In this study, we investigated the thermal performance of PV modules installed in a real scale experimental building over a traditional clay tile pitched roof in Italy for almost one year (from August 2009 to June 2010). One PV module was rack-mounted over the roof covering with a 0.2 m air gap; the others were fully integrated and installed at the same level of the roof covering (one with an air gap of 0.04 m, the other mounted directly in contact with the insulation). Temperature and heat flux measurements for each panel, and environmental parameters were recorded.Experimental results demonstrate that even though the rack-mounted PV module constantly maintains cell temperature below that of the other full-building integrated modules, due to the presence of a higher air gap, the difference in the energy produced by the PV modules estimated for the entire monitoring period is less than 4%

Nonlinear diffusion & thermo-electric coupling in a two-variable model of cardiac action potential

This work reports the results of the theoretical investigation of nonlinear dynamics and spiral wave breakup in a generalized two-variable model of cardiac action potential accounting for thermo-electric coupling and diffusion nonlinearities. As customary in excitable media, the common Q10 and Moore factors are used to describe thermo-electric feedback in a 10-degrees range. Motivated by the porous nature of the cardiac tissue, in this study we also propose a nonlinear Fickian flux formulated by Taylor expanding the voltage dependent diffusion coefficient up to quadratic terms. A fine tuning of the diffusive parameters is performed a priori to match the conduction velocity of the equivalent cable model. The resulting combined effects are then studied by numerically simulating different stimulation protocols on a one-dimensional cable. Model features are compared in terms of action potential morphology, restitution curves, frequency spectra and spatio-temporal phase differences. Two-dimensional long-run simulations are finally performed to characterize spiral breakup during sustained fibrillation at different thermal states. Temperature and nonlinear diffusion effects are found to impact the repolarization phase of the action potential wave with non-monotone patterns and to increase the propensity of arrhythmogenesis

Charge density waves enhance the electronic noise of manganites

The transport and noise properties of Pr_{0.7}Ca_{0.3}MnO_{3} epitaxial thin films in the temperature range from room temperature to 160 K are reported. It is shown that both the broadband 1/f noise properties and the dependence of resistance on electric field are consistent with the idea of a collective electrical transport, as in the classical model of sliding charge density waves. On the other hand, the observations cannot be reconciled with standard models of charge ordering and charge melting. Methodologically, it is proposed to consider noise-spectra analysis as a unique tool for the identification of the transport mechanism in such highly correlated systems. On the basis of the results, the electrical transport is envisaged as one of the most effective ways to understand the nature of the insulating, charge-modulated ground states in manganites.Comment: 6 two-column pages, 5 figure

Polar catastrophe and electronic reconstructions at the LaAlO3/SrTiO3 interface: evidence from optical second harmonic generation

The so-called "polar catastrophe", a sudden electronic reconstruction taking place to compensate for the interfacial ionic polar discontinuity, is currently considered as a likely factor to explain the surprising conductivity of the interface between the insulators LaAlO3 and SrTiO3. We applied optical second harmonic generation, a technique that a priori can detect both mobile and localized interfacial electrons, to investigating the electronic polar reconstructions taking place at the interface. As the LaAlO3 film thickness is increased, we identify two abrupt electronic rearrangements: the first takes place at a thickness of 3 unit cells, in the insulating state; the second occurs at a thickness of 4-6 unit cells, i.e., just above the threshold for which the samples become conducting. Two possible physical scenarios behind these observations are proposed. The first is based on an electronic transfer into localized electronic states at the interface that acts as a precursor of the conductivity onset. In the second scenario, the signal variations are attributed to the strong ionic relaxations taking place in the LaAlO3 layer

Correlation between choriocapillaris density and retinal sensitivity in age-related macular degeneration

Purpose: The purpose of this study was to investigate the relationship between perfusion of the choriocapillaris (CC) and retinal sensitivity in eyes with intermediate agerelated macular degeneration (iAMD). Methods: This prospective study included patients with iAMD and healthy controls. All enrolled subjects underwent optical coherence tomography angiography (OCT-A) in order to compute the percent perfused choriocapillaris area (PPCA). In patients with iAMD, microperimetry (MP) testing was performed in order to quantify: mean retinal sensitivity (MRS), over an area of 10 degrees; mean macular sensitivity (MMS), over the macular area scanned with OCT-A; and retinal sensitivity (RS) in each macular point. Results: Eighteen eyes of 13 patients were included in the analysis. In addition, 18 eyes of 12 healthy subjects were enrolled as controls. No statistically significant difference (P value > 0.2) was observed in age between patients (73.9 ± 2.0 years) and controls (70.1 ± 2.8 years). We observed significantly lower values of PPCA between patients with iAMD and healthy controls (42.0% ± 3.8% vs. 66.4% ± 3.0%; -Β = 23.8%; P value < 0.001). Among iAMD eyes, higher values of PPCA were significantly associated with higher values of MRS (P value=0.002) and MMS (P value=0.013). Finally, higher values of RS in eachmacular point analyzedwithMPwere significantly (P value<0.001) associated with higher values of PPCA computed in circular regions of interest (ROIs) centered in each analyzed MP point with radii of 0.5 degrees and 1.0 degree. Conclusions: Using OCT-A, we demonstrated a significant association between CC impairment and macular dysfunction, quantified by MP, in iAMD eyes. Translational Relevance: OCT-A could be a useful tool for detecting CC alterations and to monitor disease progression

Divergent behavior of hydrogen sulfide pools and of the sulfur metabolite lanthionine, a novel uremic toxin, in dialysis patients.

Dialysis patients display a high cardiovascular mortality, the causes of which are still not completely explained, but are related to uremic toxicity. Among uremic toxins, homocysteine and cysteine are both substrates of cystathionine β-synthase and cystathionine γ-lyase in hydrogen sulfide biosynthesis, leading to the formation of two sulfur metabolites, lanthionine and homolanthionine, considered stable indirect biomarkers of its production. Hydrogen sulfide is involved in the modulation of multiple pathophysiological responses. In uremia, we have demonstrated low plasma total hydrogen sulfide levels, due to reduced cystathionine γ-lyase expression. Plasma hydrogen sulfide levels were measured in hemodialysis patients and healthy controls with three different techniques in comparison, allowing to discern the different pools of this gas. The protein-bound (the one thought to be the most active) and acid-labile forms are significantly decreased, while homolanthionine, but especially lanthionine, accumulate in the blood of uremic patients. The hemodialysis regimen plays a role in determining sulfur compounds levels, and lanthionine is partially removed by a single dialysis session. Lanthionine inhibits hydrogen sulfide production in cell cultures under conditions comparable to in vivo ones. We therefore propose that lanthionine is a novel uremic toxin. The possible role of high lanthionine as a contributor to the genesis of hyperhomocysteinemia in uremia is discusse

Synchrotron Emission from Hot Accretion Flows and the Cosmic Microwave Background Anisotropy

Current estimates of number counts of radio sources in the frequency range where the most sensitive Cosmic Microwave Background (CMB) experiments are carried out significantly under-represent sources with strongly inverted spectra. Hot accretion flows around supermassive black holes in the nuclei of nearby galaxies are expected to produce inverted radio spectra by thermal synchrotron emission. We calculate the temperature fluctuations and power spectra of these sources in the Planck Surveyor 30 GHz energy channel, where their emission is expected to peak. We find that their potential contribution is generally comparable to the instrumental noise, and approaches the CMB anisotropy level at small angular scales. Forthcoming CMB missions, which will provide a large statistical sample of inverted-spectra sources, will be crucial for determining the distribution of hot accretion flows in nearby quiescent galactic nuclei. Detection of these sources in different frequency channels will help constrain their spectral characteristics, hence their physical properties.Comment: 10 pages, 4 figures, accepted for publication in Ap

controlled inlet airflow in ventilated facades a numerical analysis

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Urinary protein excretion rate is the best independent predictor of ESRF in non-diabetic proteinuric chronic nephropathies

Urinary protein excretion rate is the best independent predictor of ESRF in non-diabetic proteinuric chronic nephropathies. We investigated the predictors of the rate of glomerular filtration rate decline (ΔGFR) and progression to end-stage renal failure (ESRF) in the 352 patients with proteinuric non-diabetic chronic nephropathies [urinary protein excretion rate (UProt) ≥ 1g/24hr, creatinine clearance 20 to 70 ml/min/1.73m2] enrolled in the Ramipril Efficacy In Nephropathy (REIN) study. Overall the GFR declined linearly by 0.46 ± 0.05 ml/min/1.73m2/month (mean rate ± sem) over a median follow-up of 23months (range 3 to 64months), and progression to ESRF was 17.3%. Using multivariate analysis, higher UProt and mean arterial pressure (MAP) independently correlated with a faster ΔGFR (P = 0.0001 and P = 0.0002, respectively) and progression to ESRF (P = 0.0001 and P = 0.003, respectively). Mean UProt and systolic blood pressure during follow-up were the only time-dependent covariates that significantly correlated with ΔGFR (P = 0.005 and P = 0.003, respectively) and ESRF (P = 0.006 and P = 0.0001, respectively). After stratification for baseline UProt, patients in the lowest tertile (UProt < 1.9g/24hr) had the slowest ΔGFR (0.16 ± 0.07 ml/min/1.73m2/month) and progression to ESRF (4.3%) as compared with patients in the middle tertile (UProt 2.0 to 3.8g/24hr; ΔGFR, 0.55 ± 0.09 ml/min/1.73m2/month, P = 0.0002; ESRF, 15.3%, P = 0.0001) and in the highest tertile (UProt 3.9 to 18.8g/24hr; ΔGFR, 0.70 ± 0.11 ml/min/1.73m2/month, P = 0.0001; ESRF, 32.5%, P = 0.0001). Both ΔGFR (P = 0.01) and progression to ESRF (P = 0.01) significantly differed even between the middle and the highest tertiles. On the contrary, stratification in tertiles of baseline MAP failed to segregate subgroups of patients into different risk levels. Patients with the highest proteinuria and blood pressure were those with the fastest progression (ΔGFR, 0.91 ± 0.23; ESRF 34.7%). Of interest, at each level of baseline MAP, a higher proteinuria was associated with a faster ΔGFR and progression to ESRF. On the other hand, at each level of proteinuria, a faster ΔGFR was associated with MAP only in the highest tertile (> 112mm Hg) and the risk of ESRF was independent of the MAP. Thus, in chronic nephropathies proteinuria is the best independent predictor of both disease progression and ESRF. Arterial hypertension may contribute to the acceleration of renal injury associated with enhanced traffic of plasma proteins. Antihypertensive drugs that most effectively limit protein traffic at comparable levels of blood pressure are those that most effectively slow disease progression and delay or prevent ESRF in proteinuric chronic nephropathies

Developing a heritage BIM shared library for two case studies in Jordan’s heritage: The House of Art in Amman and the Qaqish House in the World Heritage City of As-Salt

International research is moving towards the development of BIM (Building Information Modelling) libraries applied to the built heritage where one of the main issues to be addressed is the modelling of complex or unique shapes that represent the specific construction components of every single asset. This perspective addresses the generation of parametric families of representative architectural geometry in the context of the management and representation of a building of heritage value. Jordan’s architectural heritage has gone through a long period of evolution and development: the result is a mixture of influences and traditions, making a great stride to conserve its buildings and Historical Heritage but has never adopted advanced digital technologies such as Building Information Modelling. In this framework, the present research aims to bridge the gap in Jordan by applying digital technologies to support heritage conservation plans by creating a 3D library of BIM objects related to typical elements of Jordanian and Arabic architecture, specifically in two cases of study. Co-production and collaboration with diverse stakeholders were central to the development of the methodology and design of the research.As a result, the first open-access HBIM shared library of historical features of Jordanian built heritage will be consolidated; this is crucial because it will set a precedent for the further documentation and conservation of the heritage of traditional cities in Jordan, MENA countries and internationally by promoting social cohesion, economic and technological development, tourism and the awareness of Jordan’s cultural heritage