Irradiated Surface Research Articles

Modeling Growth and Photoadaptation of Porphyridium purpureum Batch Culture

The work focuses on mathematical modeling of linear growth marine red algae Porphyridium purpureum batch culture under various surface irradiation. Before starting the batch culture P. purpureum was maintained for 3–5 days in turbidostat, which allowed the culture to adapt to a given light intensity. On each batch curve the maximum specific growth rate and maximum productivity are determined by approximating the exponential and linear growth phases with the appropriate equations. It is taken into account that at the beginning of the linear growth phase the integral light absorption coefficient, calculated from the true absorption spectrum in PAR range, exceeded 50 %. It is shown that with light intensity increase from 15 to 227 µmol photons m–2·s–1 the maximum specific growth rate increased from 0.31 to 1 day–1, the maximum productivity increased from 1.32 to 16.38 g DW m–2·day–1. Mathematical modeling of the linear growth of P. purpureum batch culture have showed that at any light intensity the specific growth rate is determined by the surface illumination, the light absorption coefficient and chlorophyll a concentration. The concept of reduced irradiation – the amount of absorbed light energy per chlorophyll a – was introduced. A linear dependence of the specific growth rate on reduced irradiation is given. The tangent of the angle of line slope is determined by the organization of the key multi-enzyme complex («metabolism bottleneck»). Parameters of this complex depend on the cells photoadaptation degree. For the first time a quantitative relationship between multi-enzyme complex parameters, light intensity and the chlorophyll / P700 ratio was established.

Intraoperative photodynamic therapy in the structure of complex treatment of patients suffering from recurrence and continued growth of intracranial meningioma

The effectiveness and safety of intraoperative photodynamic therapy in patients with recurrent intracranial meningiomas were examined. Intraoperative photodynamic therapy was performed in three patients suffering from relapse and continued growth of histologically confirmed intracranial meningiomas of supratentorial localization. Intraoperative photodynamic therapy was conducted with consent from patients and was confirmed by a medical commission. We used a photosensitizer of the chlorin e6 group — photoditazine (Veta-Grand, Russia). The drug was administered intravenously at a dose of 1 mg/kg during induction of anesthesia. For irradiation, laser installation Latus (ATKUS, St. Petersburg, Russia) with a power of 2.5 W and wavelength of 662 nm was used. Irradiation was conducted in a continuous mode; the duration of therapy depended on the area of the irradiated surface based on a therapeutic light dose of 180 J/cm2. In the early postoperative period, the patients’ eyes were protected for 24 h from exposure to direct sunlight, and clinical, laboratory, and intrascopic controls were carried out. No complications associated with intraoperative photodynamic therapy were observed in the early postoperative period. On control intrascopy (magnetic resonance imaging in DWI, Flair, T2, T1 + contrast modes), data showing the therapeutic effect of intraoperative photodynamic therapy were obtained. In two cases, changes in tumor tissue and its matrix were confirmed pathomorphologically, indicating the therapeutic effect of intraoperative photodynamic therapy in relation to local control of meningiomas. Thus, the use of intraoperative photodynamic therapy in the complex treatment of patients suffering from a recurrent course of the neoplastic process (“aggressive” meningiomas) reveals its effectiveness for increasing the degree of radicality of the operation and safety. Further development of the technology of intraoperative photodynamic therapy is crucial in treating patients with “aggressive” meningiomas.

Attributing the Decline of Evapotranspiration over the Asian Monsoon Region during the Period 1950–2014 in CMIP6 Models

Evapotranspiration (ET) accounts for over half of the moisture source of Asian monsoon rainfall, which has been significantly altered by anthropogenic forcings. However, how individual anthropogenic forcing affects the ET over monsoonal Asia is still elusive. In this study, we found a significant decline in ET over the Asian monsoon region during the period of 1950–2014 in Coupled Model Intercomparison Project Phase 6 (CMIP6) models. The attribution analysis suggests that anthropogenic aerosol forcing is the primary cause of the weakening in ET in the historical simulation, while it is only partially compensated by the strengthening effect from GHGs, although GHGs are the dominant forcings for surface temperature increase. The physical mechanisms responsible for ET changes are different between aerosol and GHG forcings. The increase in aerosol emissions enhances the reflection and scattering of the downward solar radiation, which decreases the net surface irradiance for ET. GHGs, on the one hand, increase the moisture capability of the atmosphere and, thus, the ensuing rainfall; on the other hand, they increase the ascending motion over the Indian subcontinent, leading to an increase in rainfall. Both processes are beneficial for an ET increase. The results from this study suggest that future changes in the land–water cycle may mainly rely on the aerosol emission policy rather than the carbon reduction policy.

Ocean surface radiation measurement best practices

Ocean surface radiation measurement best practices have been developed as a first step to support the interoperability of radiation measurements across multiple ocean platforms and between land and ocean networks. This document describes the consensus by a working group of radiation measurement experts from land, ocean, and aircraft communities. The scope was limited to broadband shortwave (solar) and longwave (terrestrial infrared) surface irradiance measurements for quantification of the surface radiation budget. Best practices for spectral measurements for biological purposes like photosynthetically active radiation and ocean color are only mentioned briefly to motivate future interactions between the physical surface flux and biological radiation measurement communities. Topics discussed in these best practices include instrument selection, handling of sensors and installation, data quality monitoring, data processing, and calibration. It is recognized that platform and resource limitations may prohibit incorporating all best practices into all measurements and that spatial coverage is also an important motivator for expanding current networks. Thus, one of the key recommendations is to perform interoperability experiments that can help quantify the uncertainty of different practices and lay the groundwork for a multi-tiered global network with a mix of high-accuracy reference stations and lower-cost platforms and practices that can fill in spatial gaps.

Retrieval of At-Surface Upwelling Radiance and Albedo by Parameterizing Cloud Scattering and Transmittance over Rugged Terrain

Accurate and continuous estimation of surface albedo is vital for assessing and understanding land–surface–atmosphere interactions. We developed a method for estimating instantaneous all-sky at-surface shortwave upwelling radiance and albedo over the Tibetan Plateau. The method accounts for the complex interplay of topography and atmospheric interactions and aims to mitigate the occurrence of data gaps. Employing an RTLSR-kernel-driven model, we retrieved surface shortwave albedo with a 1 km resolution, incorporating direct, isotropic diffuse; circumsolar diffuse; and surrounding terrain irradiance into the all-sky solar surface irradiance. The at-surface upwelling radiance and surface shortwave albedo estimates were in satisfactory agreement with ground observations at four stations in the Tibetan Plateau, with RMSE values of 56.5 W/m2 and 0.0422, 67.6 W/m2 and 0.0545, 98.6 W/m2 and 0.0992, and 78.0 98.6 W/m2 and 0.639. This comparison indicated an improved accuracy of at-surface upwelling radiance and surface albedo and significantly reduced data gaps. Valid observations increased substantially in comparison to the MCD43A2 data product, with the new method achieving an increase ranging from 40% to 200% at the four stations. Our study demonstrates that by integrating terrain, cloud properties, and radiative transfer modeling, the accuracy and completeness of retrieved surface albedo and radiance in complex terrains can be effectively improved.

Light-Field Optimization of Deep-Ultraviolet LED Modules for Efficient Microbial Inactivation

Public awareness of preventing pathogenic microorganisms has significantly increased. Among numerous microbial prevention methods, the deep-ultraviolet (DUV) disinfection technology has received wide attention by using the nitride-based light-emitting diode (LED). However, the light extraction efficiency of DUV LEDs and the utilization rate of emitted DUV light are relatively low at the current stage. In this study, a light distribution design (referred to as the reflective system) was explored to enhance the utilization of emitted DUV from LEDs, leading to successful and efficient surface and air disinfection. Optical power measurements and microbial inactivation tests demonstrated an approximately 79% improvement in average radiation power density achieved by the reflective system when measured at a 5 cm distance from the irradiation surface. Moreover, a statistically significant enhancement in local surface disinfection was observed with low electric power consumption. The reflective system was integrated into an air purifier and underwent air disinfection testing, effectively disinfecting a 3 m3 space within ten minutes. Additionally, a fluorine resin film at the nanolevel was developed to protect the light module from oxidation, validated through a 1200 h accelerated aging test under humid conditions. This research offers valuable guidance for efficient and energy-saving DUV disinfection applications.

Detecting clear‐sky periods from photovoltaic power measurements

AbstractA method for detecting clear‐sky periods from photovoltaic (PV) power measurements is presented and validated. It uses five tests dealing with parameters characterizing the connections between the measured PV power and the corresponding clear‐sky power. To estimate clear‐sky PV power, a PV model has been designed using as inputs downwelling shortwave irradiance and its direct and diffuse components received at ground level under clear‐sky conditions as well as reflectivity of the Earth's surface and extraterrestrial irradiance, altogether provided by the McClear service. In addition to McClear products, the PV model requires wind speed and temperature as inputs taken from ECMWF twentieth century reanalysis ERA5 products. The performance of the proposed method has been assessed and validated by visual inspection and compared to two well‐known algorithms identifying clear‐sky periods with broadband global and diffuse irradiance measurements on a horizontal surface. The assessment was carried out at two stations located in Finland offering collocated 1‐min PV power and broadband irradiance measurements. Overall, total agreement ranges between 84% and 97% (depending on the season) in discriminating clear‐sky and cloudy periods with respect to the two well‐known algorithms serving as reference. The disagreement fluctuating between 6% and 15%, depending on the season, primarily occurs while the PV module temperature is adequately high and/or when the sun is close to the horizon with many more interactions between the radiation, the atmosphere and the ground surface.

Dynamics of phase transformations in Si and Ge upon strong excitation with UV femtosecond laser pulses

Femtosecond laser processing of semiconductors has evolved into a mature, high-precision fabrication technique, enabling a wide range of applications. While initially most studies have employed pulses at near infrared wavelengths, the interest in using UV laser pulses is constantly increasing due to the different excitation conditions as a consequence of the much shorter optical penetration depth, leading to an improved resolution. In this context, fundamental studies on the temporal dynamics of phase transformations triggered by such pulses are necessary in order to comprehend and eventually control the complex phase transformation pathways. Here, we report a detailed time-resolved study on the phase transformation dynamics of crystalline silicon and germanium upon irradiation with single 400 nm, 100 fs laser pulses in the moderate and high excitation regime. To this end, we have employed fs-resolved optical microscopy with a probe wavelength of 800 nm to study the reflectivity evolution of the irradiated surface over a temporal window ranging from 100 fs up to 20 ns. At moderate excitation fluence, the data reveals the entire sequence of laser-induced processes, starting from the generation of a free-electron plasma, non-thermal melting, ablation onset and expansion of a semi-transparent ablation layer with sharp interfaces. At excitation with peak fluences more than 30 times the ablation threshold, an anomalous transient high-reflectivity state is observed, which might be indicative of a recoil pressure-induced liquid–liquid phase transition. Moreover, 70 nm-thick amorphous surface layers are formed in both materials after irradiation at moderate fluences. Overall, our results provide relevant information on both, transformation dynamics and final state of both materials for fs-pulse excitation in the near-UV wavelength range.

PDRs4All

Context. JWST has taken the sharpest and most sensitive infrared (IR) spectral imaging observations ever of the Orion Bar photodis-sociation region (PDR), which is part of the nearest massive star-forming region the Orion Nebula, and often considered to be the ‘prototypical’ strongly illuminated PDR. Aims. We investigate the impact of radiative feedback from massive stars on their natal cloud and focus on the transition from the H II region to the atomic PDR – crossing the ionisation front (IF) –, and the subsequent transition to the molecular PDR – crossing the dissociation front (DF). Given the prevalence of PDRs in the interstellar medium and their dominant contribution to IR radiation, understanding the response of the PDR gas to far-ultraviolet (FUV) photons and the associated physical and chemical processes is fundamental to our understanding of star and planet formation and for the interpretation of any unresolved PDR as seen by JWST. Methods. We used high-resolution near-IR integral field spectroscopic data from NIRSpec on JWST to observe the Orion Bar PDR as part of the PDRs4All JWST Early Release Science programme. We constructed a 3″ × 25″’ spatio-spectral mosaic covering 0.97– 5.27 μm at a spectral resolution R of ~2700 and an angular resolution of 0.075″–0.173″. To study the properties of key regions captured in this mosaic, we extracted five template spectra in apertures centred on the three H2 dissociation fronts, the atomic PDR, and the H II region. This wealth of detailed spatial-spectral information was analysed in terms of variations in the physical conditions-incident UV field, density, and temperature – of the PDR gas. Results. The NIRSpec data reveal a forest of lines including, but not limited to, He I, H I , and C I recombination lines; ionic lines (e.g. Fe III and Fe II); O I and N I fluorescence lines; aromatic infrared bands (AIBs, including aromatic CH, aliphatic CH, and their CD counterparts); pure rotational and ro-vibrational lines from H2; and ro-vibrational lines from HD, CO, and CH+, with most of them having been detected for the first time towards a PDR. Their spatial distribution resolves the H and He ionisation structure in the Huygens region, gives insight into the geometry of the Bar, and confirms the large-scale stratification of PDRs. In addition, we observed numerous smaller-scale structures whose typical size decreases with distance from θ1 Ori C and IR lines from C I , if solely arising from radiative recombination and cascade, reveal very high gas temperatures (a few 1000 K) consistent with the hot irradiated surface of small-scale dense clumps inside the PDR. The morphology of the Bar, in particular that of the H2 lines, reveals multiple prominent filaments that exhibit different characteristics. This leaves the impression of a ‘terraced’ transition from the predominantly atomic surface region to the CO-rich molecular zone deeper in. We attribute the different characteristics of the H2 filaments to their varying depth into the PDR and, in some cases, not reaching the C+/C/CO transition. These observations thus reveal what local conditions are required to drive the physical and chemical processes needed to explain the different characteristics of the DFs and the photochemical evolution of the AIB carriers. Conclusions. This study showcases the discovery space created by JWST to further our understanding of the impact radiation from young stars has on their natal molecular cloud and proto-planetary disk, which touches on star and planet formation as well as galaxy evolution.

Comparisons of Underwater Light From Atmospheric and Mechanically Stimulated Bioluminescence Sources in High Arctic Polar Night

AbstractAt high latitudes, polar night is a prolonged period of seasonal darkness with the sun remaining below the horizon throughout the diel cycle for up to 177 days at the North Pole. Along with diffuse atmospheric light from the sun and the moon, bioluminescence is an in‐water light source that can facilitate ecological interactions in an otherwise dim‐light environment. At high latitudes during polar night, bioluminescence rather than sunlight represents a significant portion of the photons available in the pelagic. We investigated depths of transition zones (called the bioluminescence transition depth) in the pelagic light field during polar night, defining the transition of a light field dominated by atmospheric irradiance, to one dominated by bioluminescent point sources. We derived relationships between values of the transition depth, bioluminescence potential, surface irradiance due to atmospheric light and the diffuse attenuation coefficient. We conducted studies for two Svalbard, Norway fjords, as well as for offshore areas located in the shelf‐break, shelf‐slope and in the Arctic basin. Based on our results for two polar nights, the transition from underwater light dominated by atmospheric sources to that dominated by bioluminescence occurs between 10 and 40 m in two Svalbard fjords, and between 18 and 60 m for offshore areas. These transition depths may be of particular importance to understanding how bioluminescence structures planktonic communities both in polar regions and at lower latitudes.

Possibility of Phase Transformation of Al2O3 by a Laser: A Review

Aluminum (Al) components of high quality often require an optimal ratio of lightness and favorable mechanical properties. In order to improve the physical-mechanical properties of Al, an aluminum oxide (Al2O3) film is usually formed on the surface of Al, which itself is characterized by high strength, hardness, corrosion resistance, and other technical properties. Unfortunately, depending on the conditions, the oxide film may be formed from different crystal phases on the Al surface, which are not always of desirable quality, i.e., the α-Al2O3 phase. The present review demonstrates that the properties of the Al2O3 film may be improved by Al processing with a laser beam according to the scheme: Al (Al alloy) → electrochemical anodizing → treatment with laser irradiation → α-Al2O3. Both Al substrate and the anodizing electrolyte affect the phase transformation of anodic Al2O3. Laser irradiation of the Al2O3 surface leads to high heating and cooling rates, which may promote the formation of a highly crystalline α-Al2O3 phase on anodic Al2O3.

Modification of the polymer PETG by 16 MeV Au ions

Commercial poly(ethylene glycol-co-1,4 cyclohexanedimethanol terephthalate) (PETG) foils were irradiated with 16 MeV Au7+ ions and the resulting modifications in the polymer chemical structure, optical properties, and surface hydrophobicity were analyzed. Under irradiation, PETG displays a redshift in the optical absorbance edge, accompanied by a decrease in the optical gap from 3.8 eV to 2.4 eV. An overall decrease of characteristic functional groups is observed with damage cross sections varying from (1–2) × 10-13 cm2. New bands are formed linked mainly to oxidation and formation of conjugated carbon–carbon double bonds. The hydrophilicity of the irradiated surfaces increases possibly due to surface oxidation.

Thermal Behavior of Solid Heated by Gaussian Moving Heat Source

In this paper, an analytical development is proposed to explicitly calculate the three-dimensional and transient temperature of a solid heated by a Gaussian moving heat source. The moving source dissipates heat in a thin layer near the irradiated surface of the solid and can be constant or pulsed or have any time evolution, depending on the application. The resulting solution requires only one convergent integral over time, which can be quickly computed numerically using, for example, a commercial formal calculation software. On the other hand, the derivative of the temperature with respect to time is fully explicit. We show that the results of the developed analytical solution are in excellent agreement with those of a numerical modeling that we performed under the same conditions. The temperature evolutions and the thermal maps are presented and commented.

Investigating the impact of physical vapour deposition of palladium on electron-irradiated silicon substrates

This study reports on the effect of resistive physical vapour deposition of Pd Schottky contacts on the defects observed in an irradiated n-type Si substrate. Deep-level transient spectroscopy (DLTS) was used in order to investigate the possible defects in Schottky diodes on the n-type Si. In this study the defects present where the diode was deposited first and then irradiated (“post irradiated”) were compared to those present where the substrate was irradiated first, and the Pd deposited after irradiation (“pre-irradiated”). In the post-irradiated material, the familiar radiation-induced defects were observed. However, in the pre-irradiated material, fourteen new defects were observed, with DLTS signatures differing from those of the defects in the post-irradiated diodes. The newly identified defects seemed to be specifically caused by the deposition of Pd contacts after irradiation of the substrate, as these defects were not observed when other metals such as Au, Ni, Al and Ag were deposited after irradiation. In this paper, we will refer to the observed effect that Pd deposition replaced the familiar radiation-induced defects in Si with the new set of defects as the “Pd effect”. Careful experiments ruled out annealing due to inadvertent heating of the sample during deposition as a possible cause. Care was taken to avoid all sources of contamination: The effect was observed for different sources of Pd and crucibles. This effect was inhibited by the presence of a thin intermediate layer of Pd or Au deposited before irradiation. We therefore conclude that the effect is only observed when Pd is deposited directly onto the irradiated Si surface. Out of the fourteen newly observed defects, four defects, with activation energy of 182, 220, 360 and 607 meV, had DLTS signatures corresponding to those of defects previously observed in Pd-containing Si. For the rest of the defects, no defects with similar DLTS signatures were found in literature. We therefore believe that the defects observed are produced by defect enhanced diffusion of Pd. Overall, the study enhances our understanding of defect behaviour in silicon-based devices, particularly under irradiation and metal deposition conditions, and reveals the unique properties and effects of Pd.

Lagrangian perspective on the expansion dynamics and shielding effect of femtosecond laser-induced copper plasma plumes

Femtosecond laser ablation of metals generates a strongly ionized plasma plume near the irradiated surface. The resulting plasma shielding effect can reduce subsequent laser energy deposition and lower nanomachining efficiency, especially during multi-pulse irradiation. Understanding the spatiotemporal evolution of the laser-induced plasma and its associated shielding effect is, therefore, crucial. A hybrid two-temperature and direct simulation Monte Carlo (TTM-DSMC) computational model is developed in this study, which synergistically couples the ultrafast laser–metal interaction physics and the plasma collisional transport. The model simulates the plasma properties including electron density, temperature dynamics, reflectivity, and energy attenuation throughout the plume expansion process from femtosecond to nanosecond timescales. A complex “penguin-shaped” plasma plume with internal shockwaves is observed due to the effects of double-pulse irradiation. Significantly enhanced plasma reflectivity and reduced laser energy deposition demonstrate the accumulated shielding effect, which increases with higher plasma density accumulation when the pulse separation is insufficient. Our model provides valuable theoretical guidance for optimizing processing parameters to enhance efficiency and precision in femtosecond laser machining. The integrated TTM-DSMC approach could also facilitate the study of laser-induced plasmas in other contexts like material characterization and nanoparticle synthesis.

Impacts of Low Energy Argon Beam on Enhancing the Surface Wettability and Electrical Performance of CA/PANI Films

This work study the impacts of argon irradiation on surface wettability of CA/PANI using home made ion source with fluences (4 × 1014, 8 × 1014, and 12 × 1014 ions cm−2). The EDX, SEM and FTIR methods verified the successful fabrication of the composites. Surface wettability, contact angle, and work of adhesion were measured for the untreated and irradiated composites. Raising the ion flux from 4 × 1014 ions.cm−2 to 12 × 1014 ions.cm−2, it decreases the contact angle of CA/PANI from 62.1° to 43.4° and increases the surface free energy from 46.7 to 63.9 mJ m−2. The results showed that the CA/PANI changed after exposed to radiation, proving that the irradiated surface properties were improved. In addition, their electrical conductivity was tested in frequency of 50 to106 Hz. When subjected to 12 × 1014 ions.cm−2, the conductivity rose from 1.1 × 10−8 S cm−1 for CA/PANI to 6.5 × 10−7 S cm−1. The results showed that the irradiated CA/PANI had better electrical and surface properties, which is crucial for many devices including batteries and supercapacitors.

Diversity of 3D APAR and LAI dynamics in broadleaf and coniferous forests: Implications for the interpretation of remote sensing-based products

Forests substantially mediate the water and carbon dioxide exchanges between terrestrial ecosystems and the atmosphere. The rate of this exchange, including evapotranspiration (ET) and gross primary production (GPP), depends mainly on the underlying vegetation type, health state, and the composition of abiotic environmental drivers. However, the complex 3D structure of forest canopies and the inherent top-view perspective of optical and thermal remote sensing complicate remote sensing-based retrievals of biotic and abiotic factors that eventually determine ET and GPP. This study investigates the sensitivity of remote sensing approaches to 3D variation of abiotic and biotic environmental drivers. We use 3D virtual scenes of two structurally different Swiss forests and the radiative transfer model DART to simulate the 3D distribution of solar irradiance and reflected radiance in the forest canopy. These simulations, in combination with LiDAR data, are used to derive the absorbed photosynthetic active radiation (APAR) and the leaf area index (LAI) in 3D space. The 3D variation of both parameters was quantified and analyzed. We then simulated images of the top-of-canopy bi-directional reflectance factor (BRF) and compared them with the hemispheric-conical reflectance factor (HCRF) data derived from HyPlant airborne imaging spectrometer measurements. The simulated BRF data was used to derive APAR and LAI, and the results were compared to their respective 3D representations. We unravel considerable spatial differences between both representations. We discuss possible reasons for the disagreement, including a potential insensitivity of the inherent top-of-canopy view for the real 3D product dynamics and limitations of the processing of remote sensing data, especially the approximation of effective surface irradiance. Our results can help understanding sources of uncertainties in remote sensing based gas exchange products and defining mitigation strategies.

Chlorination mechanism of typical metallic radionuclides by HCl on irradiated graphite surface from first principles

Radioactive activity of metallic radionuclides accounts for a considerable proportion in irradiated graphite from nuclear reactors. Chlorination roasting is a promising method to remove metallic radionuclides in decommissioned irradiated graphite. The decontamination effect and chlorination mechanism of 90Sr and 60Co by HCl over an irradiated graphite surface were estimated by density functional theory. 90Sr and 60Co could be chlorinated via X(signifying metallic radionuclide)→XCl→XCl2 reaction pathway. The rate-determining step appeared where metallic radionuclides desorbed from the irradiated graphite surface. The chlorination energy barriers of 90Sr and 60Co were 236 and 575 kJ/mol, respectively, implying that chlorination roasting method for decontaminate of 90Sr and 60Co in the irradiated graphite was feasible. This work is beneficial to the application of chlorination roasting for removal of metallic radionuclides in irradiated graphite.

Effects of laser pretreatment on the formation of nanostructured carbon on the surface of chlorinated polyvinyl chloride under high-power ion beam irradiation

The features of formation of surface morphology of chlorinated polyvinyl chloride (pure and with the addition of the catalyst - ferrocene) under the influence of a high-power ion beam of nanosecond duration after the preliminary pulsed laser treatment of the polymer surface have been investigated. It was found that the morphology of the irradiated surface of chlorinated polyvinyl chloride after pulsed laser surface pretreatment differs significantly from the morphology of the irradiated surface of chlorinated polyvinyl chloride after a preliminary stationary heat treatment. For pure chlorinated polyvinyl chloride, pulsed laser pretreatment with increasing power leads to an increase in the porosity of the surface layer after high-power ion beam irradiation, whereas different surface morphologies, including fibers (including polymer fibers) of different diameters, can be obtained for the pre-stationary post-irradiation thermal treatment of this polymer. Pre-stationary thermal pretreatment of chlorinated polyvinyl chloride with the addition of ferrocene (Fe(C5H5)2) leads to a decrease in the diameter of formed carbon nanofibers (with an increase in the treatment temperature). During the pulsed laser pretreatment, an increase in the porosity of the treated layer and a slight increase in the proportion of nanofibers of larger diameter are observed. To explain the obtained differences for pulsed laser and stationary thermal pretreatment, the effect of polymer heating rate on the features of chlorinated polyvinyl chloride decomposition was analyzed.

Reconstructing hyper-spectral downwelling irradiance from multi-spectral measurements

Checking the radiometric calibration of satellite hyper-spectral sensors such as the PACE Ocean Color Instrument (OCI) while they operate in orbit and evaluating remote sensing reflectance, the basic variable from which a variety of optical and biogeochemical ocean properties can be derived, requires measuring upwelling radiance just above the surface (Lw) and downwelling planar irradiance reaching the surface (Es). For this, the current HyperNav systems measure Lw at about 2 nm spectral resolution in the ultraviolet to near infrared, but Es in only four 10 nm wide spectral bands centered on 412, 489, 555, and 705 nm. In this study, the Es data acquired in these spectral bands in clear sky conditions are used to reconstruct via a multi-linear regression model the hyper-spectral Es signal at 0.5 nm resolution from 315 to 900 nm, the OCI spectral range, allowing an estimate of Es at the HyperNav, OCI, and other sensors’ resolutions. After correction of gaseous absorption and normalization by the top-of-atmosphere incident solar flux, the atmospheric diffuse transmittance is expressed as a linear combination of Es measured in those 4 spectral bands. Based on simulations for Sun zenith angles from 0 to 75° and a wide range of (i.e., expected) atmospheric, surface, and water conditions, the Es spectrum is reconstructed with a bias of less than 0.4% in magnitude and an RMS error (RMSE) ranging from 0% to 2.5%, depending on wavelength. The largest errors occur in spectral regions with strong gaseous absorption. In the presence of typical noise on Es measurements and uncertainties on the ancillary variables, the bias and RMSE become −2.5% and 7.0%, respectively. Using a General Additive Model with coefficients depending on Sun zenith angle and aerosol optical thickness at 550 nm improves statistical performance in the absence of noise, especially in the ultraviolet, but provides similar performance on noisy data, indicating more sensitivity to noise. Adding spectral bands in the ultraviolet, e.g., centered on 325, 340, and 380 nm, yields marginally more accurate results in the ultraviolet, due to uncertainties in the gaseous transmittance. Comparisons between the measured and reconstructed Es spectra acquired by the MOBY spectroradiometer show agreement within predicted uncertainties, i.e., biases less than 2% in magnitude and RMS differences less than 5%. Reconstruction can also be achieved accurately with other sets of spectral bands and extended to cloudy conditions since cloud optical properties, like aerosol properties, tend to vary regularly with wavelength. These results indicate that it is sufficient, for many scientific applications involving hyper-spectral Es, to measure Es in a few coarse spectral bands in the ultraviolet to near infrared and reconstruct the hyperspectral signal using the proposed multivariate linear modeling.