Initial Chemical Composition Research Articles

High-solids enzymatic hydrolysis of biomass: Hydrodynamics and reaction kinetics integration via numerical modeling

This study presents a novel computational fluid dynamics (CFD) model to investigate important aspects of the complex high-solids enzymatic hydrolysis (HSEH) process. The uniqueness of this CFD model lies in integrating the biochemical reaction taking place in the secondary phase and the corresponding mass transfer of the products from the secondary phase to the non-Newtonian primary phase, while dual axial impellers blend the multiphase system. The distribution of the reactants and products in the non-Newtonian primary phase affects the overall conversion of glucan to glucose, which, in turn, affects the commercial deployment of these systems for the production of renewable sugars. We investigated the effect of slurry viscosity on insoluble and soluble solids distribution, the impact of initial insoluble solids loading on total solids distribution, and varying the initial chemical composition of the insoluble solids on the total solids distribution. The comprehensive CFD model results show that variations in the chemical composition of the insoluble solids and the solids loading can each have a pronounced effect on the distribution of solids. This behavior would then affect the rate and extent of conversion of insoluble solids to soluble solids. Thus, the comprehensive CFD model can account for the interactions between independent variables, facilitating the design of small and large-scale reactors, while improving the conversion of insoluble solids to soluble solids. This novel CFD model thus represents the combined effects of key factors that influence HSEH in a realistic process environment.

Impact of agronomic and organic characteristics of waste composts from Togo on Zea mays L. nutrients contents under water stress

Drought and soils poverty considerably decreased agriculture yields in Togo. In this context, the use of wastes' composts as organic amendments presents the advantages to increase crops' yields and improve the fertility of soils while valorizing wastes. However, the effects of wastes' composts on the growth of plants highly depend on their quality, specifically on their chemical properties and the organic matter maturity. In this study, three different wastes' composts were prepared by mixing household wastes and food wastes with admixtures as natural phosphate and manure. The composts produced were analyzed according to agronomic parameters before applying a leaching test to specially assess the organic matter maturity by considering its hydrophobic and aromatic characters. Whatever the compost, the contents in organic matter and nutrients were comparable to composts usually commercialized in Togo. Their characteristics depended on their initial chemical composition. The higher the food wastes percentage, the higher the organic matter content and the addition of admixtures considerably increased the percentages in nutrients in the final product. Besides, a slightly acidic pH, a high redox potential and a low aromatic and hydrophobic organic matter were recorded for compost of food wastes unlike household wastes and mixed composts and the highest concentrations in trace metals were quantified in compost of household wastes. Agronomic tests were performed on maize (Zea mays L.) under two water regimes to evaluate the impact of the characteristics of composts on both maize's nutrition and adaptation to water stress. The chemical characteristics of composts and the maturity of organic matter highly impacted the absorption of macronutrients by plants. A slightly acidic pH and a high redox potential improved the transfer of nutrients from soils to plants under normal irrigation conditions. On the contrary, a higher aromaticity of organic matter promoted the absorption of nutrients under water stress. Wastes' composts can thus be relevantly used to improve the nutrition of plants in function of the irrigation conditions.

Contrasting responses of DOM leachates to photodegradation observed in plant species collected along an estuarine salinity gradient

A series of abiotic processes affected by salinity changes involve light-mediated reactions and different degradation pathways of organic compounds, including altered photo-oxidation, photo-degradation, and photolysis of organic matter (OM). Sunlight is known to degrade, oxidize, or mineralize dissolved organic matter (DOM) in waterways, creating large changes in compositional structure of DOM near the water surface and ultimately in the mixed layer. DOM derived from various vegetation types has differing levels of susceptibility to photolytic degradation depending on initial chemical composition and in what matrix degradation takes place (e.g., salinity). The effect of sunlight and salinity on degradation of leached DOM derived from three dominant vegetative species, Avicennia germinans, Juncus romerianus, and Taxodium distichum, along a riverine continuum in northeast Florida was determined. Leachates from these three sources in a deionized or seawater matrix were irradiated in a continuous flow-through photolytic system over the course of 20 h. Avicennia germinans and Juncus roemerinaus DOM readily degraded as indicated by decreases in absorbance across all wavelengths during the irradiation period, while Taxodium distichum DOM was found to increase in absorbance across all wavelengths in the freshwater matrix, but not in seawater. PARAFAC analysis indicated differences in photochemical components and % change of absorbance and fluorescence over time indicate the importance and variability of individual contributions to the DOM pool across an estuarine continuum. This work characterizes the photochemical properties of three individual DOM sources, exhibits the need for further research on this topic, and explores the salinity effect on photo-degradation of DOM from unique plant-derived DOM.

Thermodynamics of the Vapor-Liquid-Solid Growth of Ternary III-V Nanowires in the Presence of Silicon.

Based on a thermodynamic model, we quantify the impact of adding silicon atoms to a catalyst droplet on the nucleation and growth of ternary III–V nanowires grown via the self-catalyzed vapor–liquid–solid process. Three technologically relevant ternaries are studied: InGaAs, AlGaAs and InGaN. For As-based alloys, it is shown that adding silicon atoms to the droplet increases the nanowire nucleation probability, which can increase by several orders magnitude depending on the initial chemical composition of the catalyst. Conversely, silicon atoms are found to suppress the nucleation rate of InGaN nanowires of different compositions. These results can be useful for understanding and controlling the vapor–liquid–solid growth of ternary III–V nanowires on silicon substrates as well as their intentional doping with Si.

Стабильность неразъемного соединения жаропрочных деформируемого никелевого и литейного интерметаллидного сплавов, полученного в условиях сверхпластичности. Часть 1

The paper presents a study of welded joints of cast intermetallic single-crystal rhenium containing VKNA-25 alloy with crystallographic orientation [001] and deformable high-temperature disk nickel alloy EP975, depending on the parameters (temperature and degree of deformation) of pressure welding under superplasticity conditions. Comparison of samples before and after heat treatment is presented. The results of X-ray micro-spectral analysis of a solid-phase joint in the welding zone and at distances of up to 140 μm are presented in comparison with the initial chemical composition of the alloys, indicating an intense course of diffusion processes. The results obtained are analyzed from the point of view of maintaining the balance of alloying, calculated by the method of G.I. Morozova (calculating the number of valence electrons per unit atomic mass of the composition), the change in the atomic mass and average electron concentration of solid-phase compounds before and after heat treatment in the welded joint zone and at distances up to 140 μm was calculated. It is shown that the alloy compositions calculated taking into account the alloying balance make it possible to obtain a high-quality one-piece connection of a disk and a blade for blisk-type structures, performed under superplasticity on an installation for high-temperature pressure welding.

Tango of celestial dancers: A sample of detached eclipsing binary systems containingg-mode pulsating components

Context.Eclipsing binary systems with components that pulsate in gravity modes (gmodes) allow for simultaneous and independent constraints of the chemical mixing profiles of stars. The high precision of the dynamical masses and radii as well as the imposition of identical initial chemical compositions and equivalent ages provide strong constraints during the modelling ofg-mode period-spacing patterns.Aims.We aim to assemble a sample ofg-mode pulsators in detached eclipsing binaries with the purpose of finding good candidates for future evolutionary and asteroseismic modelling. In addition, we present a case study of the eclipsing binary KIC9850387, identified as our most promising candidate, and detail the results of the observational spectroscopic, photometric, and asteroseismic analysis of the system.Methods.We selected all of the detached eclipsing binaries in theKeplereclipsing binary catalogue withKeplerInput Catalogue (KIC) temperatures between 6000 K and 10 000 K, and performed a visual inspection to determine the presence and density ofgmodes, and the presence ofg-mode period-spacing patterns in their frequency spectra. We then characterised our sample based on theirg-mode pulsational parameters and binary and atmospheric parameters. A spectroscopic follow-up of our most promising candidate was then performed, and the orbital elements of the system were extracted. We then performed spectral disentangling followed by atmospheric modelling and abundance analysis for the primary star. We utilised an iterative approach to simultaneously optimise the pulsational and eclipse models, and subsequently performed an analysis of the pressure- (p-) andg-mode pulsational frequencies.Results.We compiled a sample of 93Keplereclipsing binary stars withg-mode pulsating components and identified clearg-mode period-spacing patterns in the frequency spectra of seven of these systems. We also identified 11 systems that contained hybridp- andg-mode pulsators. We found that theg-mode pulsational parameters and the binary and atmospheric parameters of our sample are weakly correlated at best, as expected for detached main-sequence binaries. We find that the eclipsing binary KIC9850387 is a double-lined spectroscopic binary in a near-circular orbit with a hybridp- andg-mode pulsating primary withMp= 1.66−0.01+0.01M⊙andRp= 2.154−0.004+0.002R⊙, and a solar-like secondary withMs= 1.062−0.005+0.003M⊙andRs= 1.081−0.002+0.003R⊙. We findℓ = 1 andℓ = 2 period-spacing patterns in the frequency spectrum of KIC9850387 spanning more than ten radial orders each, which will allow for stringent constraints of stellar structure during future asteroseismic modelling.

Effects of local nonequilibrium in rapid eutectic solidification—Part 1: Statement of the problem and general solution

Numerous experimental data on the rapid solidification of eutectic systems exhibit the formation of metastable solid phases with the initial (nominal) chemical composition. This fact is explained by suppression of eutectic decomposition due to diffusionless (chemically partitionless) solidification beginning at a high but a finite growth velocity of crystals. A model considering the diffusionless growth is developed in the present work to analyze the atomic diffusion ahead of lamellar eutectic couples growing into supercooled liquid. A general solution of the model is presented from which two regimes are followed. The first presents a diffusion‐limited regime with the existence of eutectic decomposition if the solid–liquid interface velocity is smaller than the characteristic diffusion speed in the bulk liquid. The second shows suppression of eutectic decomposition under diffusionless transformation from liquid to one‐phase solid if the solid–liquid interface velocity overcomes characteristic diffusion speed in the bulk liquid.

Self-ligating brackets and friction in vivo : micro-morphological and chemical assessment of active slot surface

The use of self-ligating brackets has largely developed in orthodontic practice thanks to numerous advantages, including the reduction of frictional forces during sliding orthodontic mechanic. Faced with scientific evidence, this advantage still seems to be debatable. Our objective was to evaluate in vivo the frictional force of self-ligating brackets by searching for micro-morphological and chemical effects on the active slot surface, after phase of alignment-leveling and after a period in the mouth. 16 brackets from four commercial brands were selected (Damon®, In-Ovation®, Smart-clip® and Carriere®). These brackets were visualized using a scanning electron microscope (SEM) and dispersive energy spectroscopy to study their surface and initial chemical composition. After a period in the mouth, these brackets were debonded and evaluated with SEM, to search topographic and chemical changes in relation to the frictional forces. After a period of three months used for dental alignment, all the brackets show considerable changes in topographic and chemical properties related to frictional forces, with deposit of organic debris whose importance is related to the initial surface different from one manufacturer to another.

Retrograde phases of former bridgmanite inclusions in superdeep diamonds

(Mg,Fe)SiO3 bridgmanite is the dominant phase in the lower mantle; however no naturally occurring samples had ever been found in terrestrial samples as it undergoes retrograde transformation to a pyroxene-type structure. To identify retrograde phases of former bridgmanite single-phase and composite inclusions of (Mg,Fe)SiO3 in a series of superdeep diamonds have been examined with electron microscopy, electron microprobe, Raman spectroscopy and X-ray diffraction techniques. Our study revealed that (Mg,Fe)SiO3 inclusions are represented by orthopyroxene. Orthopyroxenes in single-phase and composite inclusions inherit initial chemical composition of bridgmanites, including a high Al and low Ni contents. In composite inclusions they coexist with jeffbenite (ex-TAPP) and olivine. The bulk compositions of these composite inclusions are rich in Al, Ti, and Fe, which are similar but not fully resembling Al-rich bridgmanite produced in experiments on the MORB composition. The retrograde origin of composite inclusions due to decomposition of Al-rich bridgmanite may be doubtful because each of observed minerals may represent coexisting HP phases, i.e. bridgmanite or ringwoodite.

The mass discrepancy in intermediate- and high-mass eclipsing binaries: The need for higher convective core masses

Context. Eclipsing, spectroscopic double-lined binary star systems are excellent laboratories for calibrating theories of stellar interior structure and evolution. Their precise and accurate masses and radii measured from binary dynamics offer model-independent constraints and challenge current theories of stellar evolution. Aims. We aim to investigate the mass discrepancy in binary stars. This is the significant difference between stellar components’ masses measured from binary dynamics and those inferred from models of stellar evolution via positions of the components in the Teff − log g Kiel diagram. We study the effect of near-core mixing on the mass of the convective core of the stars and interpret the results in the context of the mass discrepancy. Methods. We fitted stellar isochrones computed from a grid of MESA stellar evolution models to a homogeneous sample of eleven high-mass binary systems. Two scenarios are considered where individual stellar components of a binary system are treated independent of each other and where they are forced to have the same age and initial chemical composition. We also study the effect of the microturbulent velocity and turbulent pressure on the atmosphere model structure and stellar spectral lines, and its link with the mass discrepancy. Results. We find that the mass discrepancy is present in our sample and that it is anti-correlated with the surface gravity of the star. No correlations are found with other fundamental and atmospheric parameters, including the stellar mass. The mass discrepancy can be partially accounted for by increasing the amount of near-core mixing in stellar evolution models. We also find that ignoring the microturbulent velocity and turbulent pressure in stellar atmosphere models of hot evolved stars results in the overestimation of their effective temperature by up to 8%. Together with enhanced near-core mixing, this can almost entirely account for the ∼30% mass discrepancy found for the evolved primary component of V380 Cyg. Conclusions. We find a strong link between the mass discrepancy and the convective core mass. The mass discrepancy can be solved by considering the combined effect of extra near-core boundary mixing and the consistent treatment in the spectrum analysis of hot evolved stars. Our binary modelling results in convective core masses between 17 and 35% of the stellar mass, which is in excellent agreement with the results from gravity-mode asteroseismology of single stars. This implies larger helium core masses near the end of the main sequence than have been anticipated so far.

Hydrometallurgical Process for Selective Extraction of Nd and Rare-Earth Metals from End-of-Life Hard Disk Drives NdFeB Magnet Scrap

This paper proposed a recycling process for neodymium-iron-boron (NdFeB) magnet scrap from the end-of-life (EOL) of hard disk drives by using hydrometallurgical process. Initial chemical composition of NdFeB magnet scrap was consisted of 25.37%Nd, 6.53%Pr, 0.90%Co, 3.63%B and 63.57%Fe. After de-magnetization and crushing into proper size, magnet scraps were directly leached by H2SO4 solution. More than 90% dissolved into acid solution with remaining small amount of residuals and Ni-coated metal. Neodymium precipitated from leached solution by pH-control to the optimum condition at pH 0.6 using NaOH solution. Solid Nd-precipitates XRD pattern was observed in form of NaNd (SO4)2.(H2O) and FeSO4.(H2O). Elemental analysis of Nd-precipitates by WD-XRF. The precipitates contained 26.50%Nd, 8.46%Pr and 1.19%Fe. In order to elimination of Fe, Nd-precipitates was leached by using H2SO4 solution to dissolve FeSO4.(H2O) into acid solution to obtain high concentration of Nd and rare-earth metals (REMs) compound. As a result, XRD pattern of Nd-compound after Fe-removal confirmed that the high purity NaNd (SO4)2.(H2O) compound was obtained. The final composition of precipitates analyzed by WD-XRF was 26.36%Nd, 8.13%Pr with Fe as low as 0.14%Fe.

How the mass and quality of wheat and vetch mulches affect drivers of soil N2O emissions

Crop residue affects nitrous oxide (N2O) emissions in no-tillage systems, but the magnitude of the emissions depends on soil drivers that are directly influenced by crop residue quality and quantity. We conducted a one-year study to investigate how mulch chemical characteristics and mass affect N2O emissions during their decomposition in the field under subtropical conditions. The mulch treatments consisted of vetch and wheat crop residues applied to the soil at quantities of 0, 3, 6 and 9 Mg ha−1 dry matter. We followed the kinetics of mulch carbon (C) and nitrogen (N), soil temperature, moisture and inorganic N, the denitrification end-product ratio [N2O/(N2O + N2)] at days 15 and 30, and N2O and carbon dioxide (CO2) emissions with a static chamber method. Mulch decomposition and C and N dynamics were very rapid for vetch and much more gradual for wheat, reflecting the differences in their initial chemical compositions, but for both residues, the initial mulch mass had no effect on the decomposition rate. The presence of mulches increased soil moisture in the 0–10 cm soil layer, with the results for water-filled pore space by treatment as 0 = 3 < 6 = 9 Mg ha−1. Vetch also significantly increased the inorganic N content in the soil, unlike wheat, which caused net N immobilization. The daily N2O fluxes were strongly and positively correlated with CO2 fluxes (r = 0.83). The highest N2O fluxes were observed in the first 60 days with the vetch residues, and the results increased by treatment as 0 < 3 < 6 = 9 Mg ha−1; for wheat, the mean N2O emitted was 50% lower than that for vetch and was not affected by mulch mass. Although the cumulative N2O emitted was higher in vetch than in wheat, the N2O emission factor was higher for the wheat than for the vetch residues (EF = 4.64% vs 1.75% of N applied). We conclude that while mulch mass and quality strongly influenced soil drivers of N2O emissions, not only the N input but also the nature of residue C and the residue location must be taken into account to understand and predict N2O emissions associated to crop residue management.

Comparison of ruminal digestibility of Origanum onites L. leaves in dairy buffalo and cows.

This experiment evaluated the ruminal digestibility of Turkish oregano leaves in dairy buffalo and cows. Ruminally cannulated, multiparous Brown Swiss cows (n = 3) and water buffalo (Bubalus bubalis; n = 3) were used in the experiment. The ad libitum basal diet was balanced to NRC requirements for a dry, nonpregnant multiparous dairy cow (680kg) and consuming 12.8kg of DM/day. Air-dried, ground, weighed oregano leaves were inserted in the rumen of all animals before the morning feeding within heat-sealed nylon bags (4 replicates per treatment and time point). After incubation (4, 8, 24, 48, and 72h), dry matter (DM), crude protein (CP), aNDFom, and ADFom concentrations were determined and compared to initial leaf chemical composition. The means for in situ disappearance (ISD, %) of DM, aNDFom, and ADFom did not differ between the species, but ISD of CP was greater in buffalo than the cows (P = 0.05) after 72h incubation. The lag time of kinetic degradation curves, the potentially degradable fraction (b), hourly degradation rate (c), and undegradable fraction were similar between species. The immediately degraded fraction (a) and effective digestibility (ED) of CP were greater in buffalo than the cows (P = 0.04), but the a fraction and ED of other nutrients showed no differences between the species. In conclusion, CP of oregano leaves are degraded more rapidly in the rumen of dairy buffalo than cows, primarily due to a large difference in the rapidly soluble CP fraction in the buffalo.

НАХОДКА МАРКЕРОВ МЕЖЛЕДНИКОВИЙ В ПЕЩЕРЕ УСЬВИНСКАЯ-1 (СРЕДНИЙ УРАЛ)1

Mineral formation due to water freezing in caves causes supersaturation of the unfrozen part of the solution and deposition of some dissolved compounds in the form of minerals. Evaporation of water and degassing of the solution are associated processes in deposition of minerals. Cryogenic minerals of caves differ in morphology and isotopic composition from similar mineral cave formations not subject to glaciation. The morphology and mineralogy of cryogenic cave minerals depend on the initial chemical composition of karst water, the thickness of the freezing layer of water, and also on the freezing rate. Slow freezing of cave waters at 0°C in permafrost conditions leads to the formation of coarse cryogenic calcite. These carbonates can be used as indicators of permafrost thawing during interglacial periods. Morphological and isotopic study of samples from Usvinskaya-1 Cave (Middle Urals), as well as their 230Th / 234U dating, made it possible to conclude that the calcite is cryogenic. The calcite is represented by aggregates (up to 5 cm in size) of split crystals and spherulites from milky brown to black in color. This calcite, formed during the interglacial periods, indicates the existence of several periods of degrading permafrost in the Middle Urals, namely in the periods MIS9 (295.7 thousand years ago), MIS7 (205.1 thousand years ago), GI23 (approx. 102-104 thousand years ago) and GI22 (89.4-90.0 thousand years ago).

The effects of leaf litter chemistry and anatomical traits on the litter decomposition rate of Quercus frainetto Ten. and Quercus cerris L. in situ

This paper presents the results of a one-year decomposition experiment on Quercus frainetto Ten. and Quercus cerris L. leaf litter in natural conditions. The decomposition rate constant was 0.831 yr?1 (Q. frainetto) and 0.458 yr?1 (Q. cerris). For the initial chemical composition of the oaks? litter, differences were not found in concentrations of lignin and fats, waxes and oil fractions, but were found for water-soluble matter, hemicellulose and cellulose. Later decomposition stages indicated that lignin and fats, waxes and oil fractions influenced differences in both oaks? litter decay rates. Anatomical analysis revealed differences between the oaks in leaf mesophyll and epidermis but not in the entire leaf and lower epidermis. Results after 12 months of the experiment revealed that 48.04% of the entire leaf, 53.30% of mesophyll, 32.93% of lignified upper and 47.67% of lower epidermis in Q. frainetto, and 28.70% of the entire leaf, 31.60% of mesophyll, 25.17% of lignified upper and 20.93% of lower epidermis in Q. cerris were decomposed. Reduction in leaf thickness mainly was caused by the reduction of mesophyll parenchyma, composed of easily degradable plant materials. Leaf tissues with the most recalcitrant plant materials were lignified upper epidermis, covered by a thick cuticle composed of fats and waxes, and xylem within the leaf veins.

Experimental Study on Pyrolysis of Non-Metallic Materials Separated from Printed Circuit Board Waste via TGA and Analytical Vacuum Fast Pyrolysis of Non-Metallic Fraction of Printed Circuit Board Waste after Copper Separation

In just over half a century electronic equipment and products have revolutionized human lifestyle. At the product’s end of life, e-waste, its components material and other materials have influenced and infiltrated environment in every part of globe. The hazardous effect of plastic materials and debris to biodiversity is well established, but mitigation and planning are often hampered by lack of quantitative data on waste accumulation patterns in landfill. Here we document a study on the pyrolysis of non-metallic material of printed circuit board, the basic elemental part of electronic waste. The non-metallic material is separated from printed circuit board waste during the copper separation processes and was found in powder form at average size up to 177 μm. The purpose of this study is to experimentally investigate the pyrolysis behavior of the non metallic material of printed circuit boards (PCB) waste fraction at a temperature range of 300 ◦C to 600 ◦C by means of the Thermogravimetric Analysis (TGA) and seek to find out the effective pyrolysis temperature that could be used in pyrolysis process in production scale. The experimental results reveal that the chemical composition of the PCB reflects that the main decomposition of PCBs occurs between 250 ◦C and 450 ◦C, and effectively decomposed at 403 ◦C. The pyrolysis of PCBs showed a varying production of aromatic compounds such as phenol, bromophenol, styrene, methylstyrene, and bisphenol A as well as non-aromatic compounds such as acetone and bromomethane, which are strongly related with the initial chemical composition of PCBs.

Influence of initial chemical composition and characteristics of pulps on the production and properties of lignocellulosic nanofibers

This work aimed to study the influence of the initial chemical composition (glucans, lignin, xylan, and mannans), intrinsic viscosity, and carboxylate groups of pulps on the production process and final properties of lignocellulosic nanofibers (LCNF). Pulps of pine sawdust, eucalyptus sawdust, and sugarcane bagasse subjected to conventional pulping and highly oxidized processes were the starting materials. The LCNF were obtained by TEMPO mediated oxidation and mechanical fibrillation with a colloidal grinder. The nanofibrillation degree, chemical charge content, rheology, laser profilometry, cristallinity and atomic force microscopy were used to characterize the LCNF. The carboxylate groups, hemicelluloses and lignin of the initial pulps were important factors that affected the production process of LCNF. The results revealed that intrinsic viscosity and carboxylate groups of the initial pulps affected LCNF production process, whereas lignin and hemicelluloses influenced the viscosity of LCNF aqueous suspensions, the roughness of LCNF films, and the carboxylate groups content of LCNF.

Raman Spectroscopy and Surface Enhanced Raman Scattering (SERS) for the Analysis of Blue and Black Writing Inks: Identification of Dye Content and Degradation Processes.

Raman spectroscopy and Surface Enhanced Raman Scattering (SERS) were applied to the analysis of blue and black writing inks. SERS was performed by application of plasmonic nanopastes constituted by Ag nanoparticles and Au nanorods directly on inks deposited on paper substrates under laser irradiation of 514 nm. It was found that SERS spectra were largely enhanced compared to Raman spectra and that Ag nanopastes produced much larger enhancements than Au nanopastes, due to a combination of plasmonic resonance, charge transfer, and molecular resonance effects. All analyzed writing inks resulted constituted by Crystal Violet and other triarylmethane dye mixtures, to which sometimes phthalocyanine dyes were also added (for example in Bic pens). SERS was also used for the identification of degradation processes occurring in artificially aged blue pens deposited on paper substrates. It was found that color alteration changed from ink to ink and varied from darkening to discoloration to slight fading, depending on the initial chemical composition. For inks containing Crystal Violet, two mechanisms associated to de-methylation and photo-reduction of excited dye to colorless leuco forms were identified.

Populations of Stellar-mass Black Holes from Binary Systems

Abstract In large and complicated stellar systems like galaxies, it is difficult to predict the number and characteristics of a black hole (BH) population. Such populations may be modeled as an aggregation of homogeneous (i.e., having uniform star formation history and the same initial chemical composition) stellar populations. Using realistic evolutionary models, we predict the abundances and properties of BHs formed from binaries in these environments. We show that the BH population will be dominated by single BHs originating from binary disruptions and stellar mergers. Furthermore, we discuss how BH populations are influenced by such factors as initial parameters, metallicity, initial mass function, and natal kick models. As an example application of our results, we estimate that about 26 microlensing events happen every year in the direction of the Galactic Bulge due to BHs in a survey like OGLE-IV. Our results may be used to perform in-depth studies related to realistic BH populations, such as observational predictions for space survey missions like Gaia or Einstein Probe. We prepared a publicly available database with the raw data from our simulations to be used for more in-depth studies.

Laser-driven direct synthesis of carbon nanodots and application as sensitizers for visible-light photocatalysis

We present the first successful synthesis of monodisperse carbon nanodots (CNDs) with tunable photoluminescence (PL) carried out by laser pyrolysis of two common volatile organic precursors such as toluene and pyridine. Remarkably, the initial chemical composition of the precursor determines the formation of undoped or N-doped CNDs and their corresponding absorption response in the visible range (expanded for the latter). We demonstrate the control and versatility of this synthesis method to tune the final outcome and its potential to explore a great number of potential solvent candidates. Furthermore, we have successfully exploited these CNDs (both undoped and N-doped) as effective sensitizers of TiO2 nanoparticles in the visible-light driven photo-degradation of a cationic dye selected as model organic pollutant.