Threshold Irradiance Research Articles

Theoretical analysis of optogenetic spiking with ChRmine, bReaChES and CsChrimson-expressing neurons for retinal prostheses

Objective. Optogenetics has emerged as a promising technique for neural prosthetics, especially retinal prostheses, with unprecedented spatiotemporal resolution. Newly discovered opsins with high light sensitivity and fast temporal kinetics can provide sufficient temporal resolution at safe light powers and overcome the limitations of presently used opsins. It is also important to formulate accurate mathematical models for optogenetic retinal prostheses, which can facilitate optimization of photostimulation factors to improve the performance. Approach. A detailed theoretical analysis of optogenetic excitation of model retinal ganglion neurons (RGNs) and hippocampal neurons expressed with already tested opsins for retinal prostheses, namely, ChR2, ReaChR and ChrimsonR, and also with recently discovered potent opsins CsChrimson, bReaChES and ChRmine, was carried out. Main results. Under continuous illumination, ChRmine-expressing RGNs begin to respond at very low irradiances ∼10−4 mW mm−2, and evoke firing upto ∼280 Hz, highest among other opsin-expressing RGNs, at 10−2 mW mm−2. Under pulsed illumination at randomized photon fluxes, ChRmine-expressing RGNs respond to changes in pulse to pulse irradiances upto four logs, although very bright pulses >1014 photons mm−2 s−1 block firing in these neurons. The minimum irradiance threshold for ChRmine-expressing RGNs is lower by two orders of magnitude, whereas, the first spike latency in ChRmine-expressing RGNs is shorter by an order of magnitude, alongwith stable latency of subsequest spikes compared to others. Further, a good set of photostimulation parameters were determined to achieve high-frequency control with single spike resolution at minimal power. Although ChrimsonR enables spiking upto 100 Hz in RGNs, it requires very high irradiances. ChRmine provides control at light powers that are two orders of magnitude smaller than that required with experimentally studied opsins, while maintaining single spike temporal resolution upto 40 Hz. Significance. The present study highlights the importance of ChRmine as a potential opsin for optogenetic retinal prostheses.

Estimation of the tolerance threshold for the irradiance of modern LED curing units when simulating clinically relevant polymerization conditions.

The study aims to characterize various LED light curing units (LED-LCU) in order to determine the tolerance threshold for varying the polymerization conditions. Two violet-blue and two blue LED-LCUs were analyzed by using a laboratory-grade spectrophotometer system. Fifty-five curing conditions were simulated in each LED-LCU by varying the position (centered and with an offset of 3-mm to the left, right, lower and upper direction) and the exposure distance (0 mm to 10 mm in 1-mm steps). Irradiance decreased with increasing exposure distance, while the effect of the LCU position was significant and LCU-specific. Only one LED-LCU enables the irradiance threshold of 1,000 mW/cm2 to be achieved in all positions up to an exposure distance of 4 mm. LCUs with a more homogeneous light beam profile more easily tolerate deviations from the ideal curing conditions. The study enables dentists to identify the limits of modern LED-LCUs and to estimate potential deviations from ideal curing conditions for clinically relevant situations.

A Coupled Lagrangian-Earth System Model for Predicting Oil Photooxidation

During the Deepwater Horizon (DWH) blowout, photooxidation of surface oil led to the formation of persistent photooxidized compounds, still found in shoreline sediments a decade later. Studies demonstrated that photooxidation modified both biodegradation rates of the surface oil and the effectiveness of aerial dispersant applications. Despite the significant consequences of this weathering pathway, the lack of measurements prevented photooxidation to be accounted for in the DWH oil budget calculations and in most predictive models. Here we develop a Lagrangian photooxidation module that estimates the dose of solar radiation individual oil droplets receive while moving in the ocean, quantifies the likelihood of photooxidative changes, and continues to track the transport of these persistent photooxidized compounds. We estimate and track the likelihood of photooxidation of Lagrangian oil droplets in the upper layers of the water column for the DWH case by coupling the net shortwave radiation from NOGAPS to the oil application of the Connectivity Modeling System (oil-CMS). The dose of solar radiation upon a droplet is computed with the intensity of the incoming irradiance at the ocean’s surface, the light attenuation coefficient, and the depth of the oil droplets. Considering a range of DWH empirical irradiance thresholds, we find that photooxidation can happen at short time scales of hours to days, in agreement with the new paradigm of oil photooxidation. Furthermore, the oxidized compounds are likely to form in a 110 km radius around the response site, suggesting that the oil reaching the coastline was already photooxidized. This new dynamic coupling provides a powerful tool to test oil weathering hypotheses, refine the oil budget during the DWH, and ultimately inform rapid response in future oil spills.

Near-Infrared Light and Skin: Why Intensity Matters.

Infrared light (760 nm-1 mm) constitutes approximately 40% of the solar radiation reaching the ground at sea level. Shortest wavelength near-infrared (NIR) photons (NIR or IR-A: 760-1,400 nm) can penetrate the epidermis, dermis, and subcutaneous tissue with numerous biological effects. NIR used to have a bad reputation on the basis of past studies using high-intensity artificial light sources (above the solar IR-A irradiance threshold) at high doses leading to detrimental effects (i.e., upregulation of matrix metalloproteinase-1). However, when looking at the other side of the coin and what we can learn from the sun, NIR intensity matters. Hence, mimicking sunlight NIR intensity (30-35 mW/cm2) will rather trigger beneficial cutaneous effects. It is likely that intensity is more important than the fluence (dose) delivered. Moreover, the law of reciprocity (i.e., the biological effect is directly proportional to the total dose irrespective of intensity) does not always apply when considering tissue response in photobiology. In fact, the biphasic dose curve (Arndt-Schulz curve) of photobiomodulation establishes that if irradiance is lower than the physiological threshold value for a given target, it does not produce beneficial effects, even when -irradiation duration is extended. Also, photo-inhibitory deleterious effects may occur at higher irradiances. Remarkably, the beneficial "sweet spot" in between corresponds to the irradiance of the sun. NIR might even precondition the skin from an evolutionary standpoint as exposure to early morning NIR wavelengths in sunlight may prepare the skin for upcoming mid-day harmful UVR. Consequently, NIR light appears to be the solution, not the problem.

Outdoor PV System Monitoring—Input Data Quality, Data Imputation and Filtering Approaches

Photovoltaic monitoring data are the primary source for studying photovoltaic plant behavior. In particular, performance loss and remaining-useful-lifetime calculations rely on trustful input data. Furthermore, a regular stream of high quality is the basis for pro-active operation and management activities which ensure a smooth operation of PV plants. The raw data under investigation are electrical measurements and usually meteorological data such as in-plane irradiance and temperature. Usually, performance analyses follow a strict pattern of checking input data quality followed by the application of appropriate filter, choosing a key performance indicator and the application of certain methodologies to receive a final result. In this context, this paper focuses on four main objectives. We present common photovoltaics monitoring data quality issues, provide visual guidelines on how to detect and evaluate these, provide new data imputation approaches, and discuss common filtering approaches. Data imputation techniques for module temperature and irradiance data are discussed and compared to classical approaches. This work is intended to be a soft introduction into PV monitoring data analysis discussing best practices and issues an analyst might face. It was seen that if a sufficient amount of training data is available, multivariate adaptive regression splines yields good results for module temperature imputation while histogram-based gradient boosting regression outperforms classical approaches for in-plane irradiance transposition. Based on tested filtering procedures, it is believed that standards should be developed including relatively low irradiance thresholds together with strict power-irradiance pair filters.

Feasibility study of a blind-type photovoltaic roof-shade system designed for simultaneous production of crops and electricity in a greenhouse

The use of renewable energy in modern greenhouse management is important to achieve efficient and sustainable food supplies for a world with increasing population. This study assessed the performance of a blind-type shading regulator that can automatically rotate semi-transparent photovoltaic (PV) blades installed on the greenhouse roof in response to sunlight variation. The PV blind oriented parallel to the roof partially blocked intense sunlight penetration into the greenhouse, but it transmitted sunlight during cloudy time by turning the blind bearing to be perpendicular to the roof. A stable irradiation environment is therefore producible in the greenhouse under variable sky conditions. Annual operations demonstrated that the blinds’ own generated electrical energy can sustain PV blind operation and produce surplus electrical energy. The PV blind electricity generation and sunlight availability for crops below the PV blind roof were calculated based on a mathematical model developed using theoretical sunlight parameters and the experimentally obtained PV blind system parameters. Assuming cloudless skies and threshold irradiance for blind rotation set at 500 W m−2, 13.0 and 12.3 kWh m−2 yr−1 surplus electrical energy can be generated, respectively, by north–south and east–west oriented model greenhouses. Cloudy skies reduce surplus electrical energy production by 50%, but PV blinds can supply greenhouse electrical energy demands partially or completely, depending on the degree of greenhouse electrification. Below the PV blinds, 8–10 MJ m−2 day−1 of insolation is expected to irradiate crops under actual sky conditions. This insolation is sufficient to cultivate major horticultural crops. Regulating the threshold irradiance level for PV blind turning can control the sunlight apportionment ratio for cultivation and electricity generation, thereby enabling sustainable energy–food dual production in a greenhouse.

Global distribution of photosynthetically available radiation on the seafloor

Abstract. A 21 year (1998–2018) continuous monthly data set of the global distribution of light (photosynthetically available radiation, PAR, or irradiance) reaching the seabed is presented. This product uses ocean color and bathymetric data to estimate benthic irradiance, offering critical improvements on a previous data set. The time series is 4 times longer (21 versus 5 years), the spatial resolution is better (pixel size of 4.6 versus 9.3 km at the Equator), and the bathymetric resolution is also better (pixel size of 0.46 versus 3.7 km at the Equator). The paper describes the theoretical and methodological bases and data processing. This new product is used to estimate the surface area of the seafloor where (1) light does not limit the distribution of photosynthetic benthic organisms and (2) net community production is positive. The complete data set is provided as 14 netCDF files available on PANGAEA (Gentili and Gattuso, 2020a, https://doi.org/10.1594/PANGAEA.910898). The R package CoastalLight, available on GitHub (https://github.com/jpgattuso/CoastalLight.git, last access: 29 July 2020), allows us (1) to download geographical and optical data from PANGAEA and (2) to calculate the surface area that receives more than a given threshold of irradiance in three regions (nonpolar, Arctic, and Antarctic). Such surface areas can also be calculated for any subregion after downloading data from a remotely and freely accessible server.

Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit

Mass-radius relationships for water-rich rocky planets are usually calculated assuming most water is present in condensed (either liquid or solid) form. Planet density estimates are then compared to these mass-radius relationships, even when these planets are more irradiated than the runaway greenhouse irradiation limit (around 1.1 times the insolation at Earth for planets orbiting a Sun-like star), for which water has been shown to be unstable in condensed form and would instead form a thick H2O-dominated atmosphere. Here we use a 1-D radiative-convective inverse version of the LMD generic numerical climate model to derive new theoretical mass-radius relationships appropriate for water-rich rocky planets that are more irradiated than the runaway greenhouse irradiation limit, meaning planets endowed with a steam, water-dominated atmosphere. As a result of the runaway greenhouse radius inflation effect introduced in previous work, these new mass-radius relationships significantly differ from those traditionally used in the literature. For a given water-to-rock mass ratio, these new mass-radius relationships lead to planet bulk densities much lower than calculated when water is assumed to be in condensed form. In other words, using traditional mass-radius relationships for planets that are more irradiated than the runaway greenhouse irradiation limit tends to dramatically overestimate -possibly by several orders of magnitude- their bulk water content. In particular, this result applies to TRAPPIST-1 b, c, and d, which can accommodate a water mass fraction of at most 2, 0.3 and 0.08%, respectively, assuming planetary core with a terrestrial composition. In addition, we show that significant changes of mass-radius relationships (between planets less and more irradiated than the runaway greenhouse limit) can be used to remove bulk composition degeneracies in multiplanetary systems such as TRAPPIST-1. Broadly speaking, our results demonstrate that non-H2/He-dominated atmospheres can have a first-order effect on the mass-radius relationships, even for rocky planets receiving moderate irradiation. Finally, we provide an empirical formula for the H2O steam atmosphere thickness as a function of planet core gravity and radius, water content, and irradiation. This formula can easily be used to construct mass-radius relationships for any water-rich, rocky planet (i.e., with any kind of interior composition ranging from pure iron to pure silicate) more irradiated than the runaway greenhouse irradiation threshold.

Comparison of low-power, high-frequency and temporally precise optogenetic inhibition of spiking in NpHR, eNpHR3.0 and Jaws-expressing neurons

A detailed theoretical analysis of low-power, high-frequency and temporally precise optogenetic inhibition of neuronal spiking, with red-shifted opsins namely, NpHR, eNpHR3.0 and Jaws, has been presented. An accurate model for inhibition of spiking in these opsins expressed hippocampal neurons that includes the important rebound activity of chloride ions across the membrane has been formulated. The effect of various parameters including irradiance, pulse width, frequency, opsin-expression density and chloride concentration has been studied in detail. Theoretical simulations are in very good agreement with reported experimental results. The chloride concentration gradient directly affects the photocurrent and inhibition capacity in all three variants. eNpHR3.0 shows smallest inhibitory post-synaptic potential plateau at higher frequencies. The time delay between light stimulus and target spike is crucial to minimize irradiance and expression density thresholds for suppressing individual spike. Good practical values of photostimulation parameters have been obtained empirically for peak photocurrent, time delay and 100% spiking inhibition, at continuous and pulsed illumination. Under continuous illumination, complete inhibition of neural activity in Jaws-expressing neurons takes place at minimum irradiance of 0.2 mW mm−2 and expression density of 0.2 mS cm−2, whereas for pulsed stimulation, it is at minimum irradiance of 0.6 mW mm−2 and 5 ms pulse width, at 10 Hz. It is shown that Jaws and eNpHR3.0 are able to invoke single spike precise inhibition up to 160 and 200 Hz, respectively. The study is useful in designing new experiments, understanding temporal spike coding and bidirectional control, and curing neurological disorders.

Irradiance, Photofrin® Dose and Initial Tumor Volume are Key Predictors of Response to Interstitial Photodynamic Therapy of Locally Advanced Cancers in Translational Models.

The objective of the present study was to develop a predictive model for Photofrin®‐mediated interstitial photodynamic therapy (I‐PDT) of locally advanced tumors. Our finite element method was used to simulate 630‐nm intratumoral irradiance and fluence for C3H mice and New Zealand White rabbits bearing large squamous cell carcinomas. Animals were treated with light only or I‐PDT using the same light settings. I‐PDT was administered with Photofrin® at 5.0 or 6.6 mg kg−1, 24 h drug‐light interval. The simulated threshold fluence was fixed at 45 J cm−2 while the simulated threshold irradiance varied, intratumorally. No cures were obtained in the mice treated with a threshold irradiance of 5.4 mW cm−2. However, 20–90% of the mice were cured when the threshold irradiances were ≥8.6 mW cm−2. In the rabbits treated with I‐PDT, 13 of the 14 VX2 tumors showed either local control or were cured when threshold irradiances were ≥15.3 mW cm−2 and fluence was 45 J cm−2. No tumor growth delay was observed in VX2 treated with light only (n = 3). In the mouse studies, there was a high probability (92.7%) of predicting cure when the initial tumor volume was below the median (493.9 mm3) and I‐PDT was administered with a threshold intratumoral irradiance ≥8.6 mW cm−2.

Neural Network-Based Classification of String-Level IV Curves From Physically-Induced Failures of Photovoltaic Modules

Accurate diagnosis of failures is critical for meeting photovoltaic (PV) performance objectives and avoiding safety concerns. This analysis focuses on the classification of field-collected string-level current-voltage (IV) curves representing baseline, partial soiling, and cracked failure modes. Specifically, multiple neural network-based architectures (including convolutional and long short-term memory) are evaluated using domain-informed parameters across different portions of the IV curve and a range of irradiance thresholds. The analysis identified two models that were able to accurately classify the relatively small dataset (~400 samples) at a high accuracy (99%+). Findings also indicate optimal irradiance thresholds and opportunities for improvements in classification activities by focusing on portions of the IV curve. Such advancements are critical for expanding accurate classification of PV faults, especially for those with low power loss (e.g., cracked cells) or visibly similar IV curve profiles.

Solar resource assessment of modern parking machines in an urban environment

This study presents a methodology for assessing the potential solar resource available at solar-powered parking machines installed in a typical city center. It is based on capturing fisheye images through an appropriate camera/lens. These images are then processed to classify the sky and non-sky pixels using a semi-automated sky detection method, also developed in this study. The processed images are then used to calculate the diffuse and beam solar potential of the site by estimating the visible fraction of the sky and the hours of the year during which the sun can be seen from the site, respectively. For the case study, 15 existing parking machines were analyzed in the central business district of Auckland (New Zealand). It was found that most of these machines were able to capture less than 50% of the available solar potential. Only two machines crossed the yearly irradiation threshold that represents the criterion for solar panel installation. If modern high-power solar-powered machines are used, selecting suitable locations for installation is crucial.

Characteristics of prosthetic vision in rats with subretinal flat and pillar electrode arrays

Objective. Retinal prostheses aim to restore sight by electrically stimulating the surviving retinal neurons. In clinical trials of the current retinal implants, prosthetic visual acuity does not exceed 20/550. However, to provide meaningful restoration of central vision in patients blinded by age-related macular degeneration (AMD), prosthetic acuity should be at least 20/200, necessitating a pixel pitch of about 50 µm or lower. With such small pixels, stimulation thresholds are high due to limited penetration of electric field into tissue. Here, we address this challenge with our latest photovoltaic arrays and evaluate their performance in vivo. Approach. We fabricated photovoltaic arrays with 55 and 40 µm pixels (a) in flat geometry, and (b) with active electrodes on 10 µm tall pillars. The arrays were implanted subretinally into rats with degenerate retina. Stimulation thresholds and grating acuity were evaluated using measurements of the visually evoked potentials (VEP). Main results. With 55 µm pixels, we measured grating acuity of 48 ± 11 µm, which matches the linear pixel pitch of the hexagonal array. This geometrically corresponds to a visual acuity of 20/192 in a human eye, matching the threshold of legal blindness in the US (20/200). With pillar electrodes, the irradiance threshold was nearly halved, and duration threshold reduced by more than three-fold, compared to flat pixels. With 40 µm pixels, VEP was too low for reliable measurements of the grating acuity, even with pillar electrodes. Significance. While being helpful for treating a complete loss of sight, current prosthetic technologies are insufficient for addressing the leading cause of untreatable visual impairment—AMD. Subretinal photovoltaic arrays may provide sufficient visual acuity for restoration of central vision in patients blinded by AMD.

Spectral influence analysis on sunshine duration measurement

Sunshine duration is an important variable in surface meteorological measurement. In this article, two methods for measuring sunshine duration are described, one is photovoltaic-based instrument, which ranges from 400 to 1100 nm, and the other is thermopile-based pyrheliometer, which ranges from 300 to 3000 nm. Due to the spectrum is more representative and accuracy for solar radiation, the pyrheliometer is recommended as the reference sensor for the detection of the threshold irradiance for defining the sunshine duration. The comparison between the photovoltaic- and thermopile-based instruments is carried out to uncover the spectral influence on sunshine duration measurement, analysis by the SMARTS tool is presented to calculate irradiance with different spectral ranges under different altitudes.

Investigation of the degradations in power GaN-on-Si MIS-HEMTs subjected to cumulative γ-ray irradiation

In this work, GaN-on-Si power Metal-Insulator-Semiconductor High Electron Mobility Transistors (MIS-HEMTs) are irradiated through different regimes of cumulative γ-ray irradiation, namely 1, 2, 3, 4, and 5 kGy for the first sample; 1, 3, and 5 kGy for the second sample; 1, 5, and 10 kGy for the third sample; and 1, 10, and 20 kGy for the fourth sample. After each irradiation dose, drain current (ID), threshold voltage (VTh), and gate leakage current (Ig) are electrically characterized in all the samples. An improvement in ID with a shift in VTh is observed in all the samples, which saturates after a higher irradiation dose. X-ray photoelectron spectroscopy (XPS) analysis confirms creation of nitrogen vacancies that act as donor and improves the ID. No significant change in Ig is observed except for an increase in noise in gate leakage current. Scanning electron microscopy (SEM) shows the Al-based metallization pad degrades due to formation of small cavities. Finally, energy dispersive X-ray (EDX) analysis confirms the formation of Al native oxides due to γ-ray irradiation.

Vacuum-semiconductor hybrid photoelectric device for near IR-region

Results of the development of a hybrid vacuum semiconductor photodetector for the near IR-range are presented. The device is based on InP/In0.53Ga0.47As/InP photocathode and electron-sensitive CCD matrix with the number of elements 768×580. In order for the minority charge carriers generated within 0.5 μm from the surface to reach the recording cells, the CCD matrix was thinned to about 30 μm. In addition, in the reverse side of the matrix the phosphorus impurity was implanted. This technique creates the necessary gradient of the electric field, which provides high efficient transport of minority charge carriers to the potential pits of the CCD matrix. At room temperature and continuous irradiation the measured threshold irradiance was registered at the level of 5·10−8 W/cm2 for the wavelength range λ = 1–1.5 μm.

Surface kinetics analysis by direct area measurement: Laser assisted dehydration of α-FeOOH

A novel method for surface kinetics analysis based solely on quantitative image analysis technique is proposed, and implemented for evaluating the activation energy, 110 (10) meV, of laser assisted dehydration of goethite. Millisecond radiative heat transfer via 785 nm laser beam, allowed us to elucidate a transient surface dehydration below 200 °C. In addition, the proposed method evaluates the laser threshold Irradiance - 1.2(1) μW/μm2 and its temperature dependence. The complementary contributions of radiative (transient) and conductive (equilibrium) heat transfer to the sample provides viable physical elucidation of the observed phenomenon - dehydrated spot surface area, variations with the laser power and the equilibrium temperature. The method allows effectively to isolate and study surface process and can be efficiently applied for any pulse laser assisted surface transformation, when the initial and final products have visual contrast.

‘Stemness’ and ‘senescence’ related escape pathways are dose dependent in lung cancer cells surviving post irradiation

AimsLung cancer is one of the main causes of cancer-related deaths worldwide and radiotherapy is a major treatment of choice. However, radioresistance is a main reason for radiotherapy failure or tumor relapse. Here, we investigated possible mechanisms associated with cancer cell radioresistance. Materials and methodsWe compared two newly derived cell lines, namely A549-IR3 and A549-IR6, which survived repeated (3 or 6 times) 4 Gy exposure of parental A549 lung cancer cell line. DNA repair ability, stemness and senescence were comparatively studied. Key findingsA549-IR3 exhibited higher proliferation ability and radioresistance compared to parental and A549-IR6 cells. Enhanced radioresistance was not accompanied by chemoresistance to cisplatin or docetaxel. DNA repair kinetics (γΗ2ΑΧ expression) were similar in all cell lines. A549-IR3 cells exhibited a significant rise in stem cell markers (CD44, CD133, OCT4, SOX2 and NANOG) whereas A549-IR6 displayed an increased senescent population. SignificanceCancer cells surviving after radiotherapy may follow two different escape pathways: selection for radioresistance resulting in regrowth, and in clinical terms relapse, or above an irradiation threshold, stem-cells die and cancer cells become senescent, leading the tumor to a state of dormancy.

Active surfaces selection method for building-integrated photovoltaics (BIPV) in renovation projects based on self-consumption and self-sufficiency

In light of the Paris Agreement's objectives and the related European and Swiss goals of decarbonising the built environment, the importance, relevance, and potential benefits of integrating Building-Integrated Photovoltaic (BIPV) within building renovation processes are acknowledged. Functioning both as envelope material and on-site electricity generator, BIPV can simultaneously reduce the use of fossil fuels and greenhouse gas emissions. Motivated by the current barriers and misconceptions that withhold a widespread integration of BIPV, particularly regarding financial implications and solar exposure levels that are believed to be unfavourable, this paper aims at bringing new knowledge and a rigorous and adaptable method to inform decision-making and promote the use of BIPV in urban renewal processes. Focusing on the architectural design, we here present a methodology to select active (BIPV) surfaces during the retrofitting process based on a trade-off between the self-consumption (SC) and self-sufficiency (SS) of a building. The approach consists in iteratively identifying surfaces that achieve a varying annual irradiation value (threshold). It also includes the evaluation of the effect of electricity storage systems. The methodology and the results of its application are presented through the comparison of two case studies in Neuchâtel (Switzerland). The outcomes of this new approach for addressing building renovation projects in the urban context can help architects, designers and engineers to better size the installation and the repartition of active surfaces in the renovated thermal envelope. Results show that it is important to take into account a larger range of irradiation levels to choose the active surfaces, especially in high-rise buildings with a greater proportion of façade than roof. In such cases, the irradiation threshold can vary between 600 and 800 kWh/m2·year depending on the strategy adopted in terms of Heating, Ventilation and Air-conditioning (HVAC) system improvement or storage system implementation. Such findings demonstrate the need for context-specific methods towards a proper evaluation and better valorisation of BIPV potential.

Determining and scaling continuous-wave, laser-induced damage thresholds of thin reflectors.

Scalable and repeatable determinations of continuous wave (CW) laser-induced damage thresholds are required to develop materials for applications ranging from deformable mirrors to momentum transfer. Current standards assume sample geometries and beam conditions where CW damage thresholds are constant in linear power density, depend strongly on substrate thermal conductivity, and are insensitive to environmental conditions. In this work, the CW laser response of thin PET films with a reflective Al/MgF2 coating are experimentally assessed over a range of beam diameters and irradiances. The laser-induced damage threshold decreases with increased exposure time down to a temporally-independent irradiance, decreases with increased beam diameter to an irradiance that is independent of spot size, and depends on radiative and convective cooling. Models are used to define the minimum spot size and exposure time required to achieve such constant damage threshold irradiances for thin reflectors.