Total Absorption Research Articles

Catalytic Peculiarity of Alkali Metal Cation-Free Electrode/Polyelectrolyte Interfaces Toward CO2 Reduction.

A prominent feature of modern electrochemical technologies, such as fuel cells and electrolysis, is the employing of polyelectrolytes instead of liquid electrolytes. Unlike the well-studied electrode/liquid electrolyte interfaces, however, the catalytic characteristics of electrode/polyelectrolyte interfaces remain largely unexplored, mostly due to the lack of reliable probing methods. Herein, we report a universally applicable approach to investigating electrocatalytic reactions at electrode/polyelectrolyte interfaces under normal electrochemical conditions. By coating a thin layer of anion-exchange membrane (AEM) onto the electrode surface, solutions with bulky organic cations were well separated, thus a pure electrode/polyelectrolyte interface can be established in a regular electrochemical setup and studied using in situ spectroscopies, e.g., attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). We found that the blank Au surface was inert toward the CO2 reduction reaction (CO2RR) in the absence of alkali metal cations, whereas coating with an AEM can dramatically turn on the catalytic activity. ATR-SEIRAS revealed that the hydrogen bond network of water at the Au/AEM interface was enhanced in comparison to that on the blank Au surface, which facilitated the hydrogenation process of the CO2RR. These findings further our fundamental understanding of the catalytic behavior of electrode/polyelectrolyte interfaces and benefit the development of relevant electrochemical technologies.

Ultra-wideband solar perfect absorber for photothermal conversion with high manufacturing error tolerance

Solar energy is a key way to solve today's energy and environmental crises, and the full collection and utilization of solar energy requires a solar absorber with a broader spectrum and higher efficiency. Here, we present a solar metamaterial absorber, consisting of a Ti substrate, a Si3N4 dielectric spacer layer, and a Ti–SiO2 patterned layer. The results of the simulation show that the average absorption of the absorber is 98.16% in the range of 200–4200 nm under normal incidence. Its high absorption is attributed to the interaction of magnetic resonance (MR), cavity resonance (CR), guided mode resonance (GMR) and surface plasmon resonance (SPR). Moreover, the total absorption of the absorber in the AM1.5 standard solar radiation spectrum is 97.8% and the total absorption of blackbody radiation at 1500 K is 98.0%. In addition, the total photothermal conversion efficiency is still 92.2% at 1000 K. The proposed metamaterial absorber is also characterized by wide-angle incidence insensitivity, polarization-independence and a high tolerance of fabrication errors, which can be practically applied in the field of solar energy harvesting.

Mn 2p and O 1s X-ray absorption spectroscopy of manganese oxides

Manganese oxides (MnOx) are used as electrode materials in many different energy storage applications such as batteries and supercapacitors. X-ray spectromicroscopy, using near edge X-ray absorption spectra (NEXAFS) for chemical speciation, is a powerful tool to study reduction and oxidation processes in such systems. High quality reference spectra are required for both qualitative identification and quantitative mapping of MnOx species. Here we present accurate, quantitative Mn 2p and O 1s NEXAFS spectra of MnO, MnSO4, Mn3O4, Mn2O3, α-MnO2, β-MnO2, and KMnO4, measured using both transmission and total electron yield X-ray absorption techniques. An example of the use of these reference spectra in a study of Zn/MnO2 batteries is given.

Insights into Electrochemical CO2 Reduction on Metallic and Oxidized Tin Using Grand-Canonical DFT and In Situ ATR-SEIRA Spectroscopy.

Electrochemical CO2 reduction (CO2R) to formate is an attractive carbon emissions mitigation strategy due to the existing market and attractive price for formic acid. Tin is an effective electrocatalyst for CO2R to formate, but the underlying reaction mechanism and whether the active phase of tin is metallic or oxidized during reduction is openly debated. In this report, we used grand-canonical density functional theory and attenuated total reflection surface-enhanced infrared absorption spectroscopy to identify differences in the vibrational signatures of surface species during CO2R on fully metallic and oxidized tin surfaces. Our results show that CO2R is feasible on both metallic and oxidized tin. We propose that the key difference between each surface termination is that CO2R catalyzed by metallic tin surfaces is limited by the electrochemical activation of CO2, whereas CO2R catalyzed by oxidized tin surfaces is limited by the slow reductive desorption of formate. While the exact degree of oxidation of tin surfaces during CO2R is unlikely to be either fully metallic or fully oxidized, this study highlights the limiting behavior of these two surfaces and lays out the key features of each that our results predict will promote rapid CO2R catalysis. Additionally, we highlight the power of integrating high-fidelity quantum mechanical modeling and spectroscopic measurements to elucidate intricate electrocatalytic reaction pathways.

Comparative study of atmospheric brown carbon at Shanghai and the East China Sea: Molecular characterization and optical properties

The pollution burdens and compositions of atmospheric brown carbon (BrC) that determine their impacts on climate-health-ecosystems have not been well studied, particularly in some mega-economic coastal areas. Herein, atmospheric BrC samples synchronously collected from urban Shanghai (SH) and Huaniao Island (HNI) in the East China Sea during winter were characterized through ultrahigh-performance liquid chromatography-diode array detector-high resolution mass spectrometry (UHPLC-DAD-HRMS). The three polarity-dependent BrC fractions exhibited significant differences in both light absorption and chromophore composition. The average light absorption coefficients of BrC subfractions at 365 nm in SH were 2.6–3.7 times higher than those in HNI. The water-insoluble BrC (WIS-BrC) and humic-likes BrC (HULIS-BrC) dominated the total BrC absorption in SH (45 ± 7 %) and HNI (43 ± 6 %), respectively. Compared with SH, the higher O/Cw, lower molecule conjugation degree, and reduced mass absorption efficiency at 365 nm (MAE365) in HNI imply a potential bleaching mechanism during the transportation oxidation process. Thousands of BrC chromophores were detected at both sites. >20 major chromophores with strong absorption were unambiguously identified in HULIS-BrC and accounted for ∼40 % of the HULIS light absorption at 365 nm at both sites. These chromophores in SH HULIS-BrC featured oxygenated aromatics and nitroaromatics, while alkyl benzenesulfonic acids with emissions from cargo ships were found in HNI HULIS-BrC. Moreover, 22 major chromophores identified in WIS-BrC included alkaloids, polyaromatic hydrocarbons (PAHs), and carbonyl oxygenated PAHs, contributing 39 % and 49 % of the WIS-BrC light absorption at 365 nm in SH and HNI, respectively. Ascertaining the molecular-specific optical properties of BrC chromophores over the mega-economic coastal area is helpful for the predictive understanding of the sources and evolution of BrC, as well as its atmospheric behavior from land to sea.

Effect of composite fin structure on phase change heat storage tank: A numerical investigation

This study investigates the phase change heat storage process in the hot water displacement system. The PCHS unit incorporates V-shaped fins and straight fins to enhance heat transfer, with the additional enhancement of annular fins. Numerical simulation is used to examine the impact of fin structure and quantity on the evolution of internal flow rate, liquid phase, and temperature during the heat charging process. The response of different fin structures to parameters such as melting time, heat storage rate, storage capacity, and dimensionless temperature is analyzed. The results indicate that Model-6 (4 V-shaped fins + annular fins) exhibits the shortest melting time, reduced by 52.13 % compared to Model-1 (initial structure). The melting time of Model-4 (4 straight fins + annular fins) and Model-6 shows little difference, during the final melting stage, attributed to the good heat transfer performance of the bottom fin in Model-4. Furthermore, the total heat absorption of Model-4 and Model-6 is decreased by 3.92 % and 3.20 % respectively compared to Model-1, while the mean rate of heat storage is increased by 100.20 % and 102.21 % compared to Model-1, demonstrating the significant improvement in heat storage performance with annular fins. Additionally, the same number of V-shaped fins and straight fins, when paired with annular fins, exhibit minimal differences in their strengthening effects, with V-shaped fins enhancing pre-melting and mid-melting, and straight fins showing advantages for end-melting.

Towards autistic flow theory: A non‐pathologising conceptual approach

AbstractFlow states are heightened moments of concentration, motivation and enjoyment, leading to total absorption in the present moment. A striking parallel exists between flow states and phenomenological accounts of autistic daily life. We analyse the components of flow theory alongside autistic autobiographical accounts to explore similarities and differences, in doing so moving toward an understanding of autistic flow theory. We highlight the considerations and opportunities this may hold for future autism research, in particular the advantage that this offers a non‐pathologising approach to researching autism, one which helps to explain contextualised behaviour (i.e., alignment between the situation and what is happening in one's mind). Drawing on autistic autobiographical accounts, we outline four principles: (1) autistic people are uniquely placed to discover and manage flow; (2) autistic flow may qualitatively diverge from traditional models of flow; (3) difficulties maintaining and exiting flow for autistic people highlight a need to examine transitions into and out of flow; and, (4) internal and external constraints to flow highlight there is unrealised autistic potential yet to be discovered. The implications of an autistic flow theory are discussed in terms of how it can impact (a) our conceptual understanding of autism providing alternative explanations to previously researched phenomena, and (b) how we build enabling environments for autistic people that allow flow to flourish across educational practice, wellbeing and research contexts.

Enhanced wave absorption due to local flexibility on wide beams using mass-spring-damper scatterers

It is known that total absorption of flexural waves in a thin beam is possible through the use of monopole-dipole scatterers. In this study, we introduce a pair of identical monopole scatterers for near-total absorption of flexural waves in a thin and wide beam. Despite the two scatterers being both of the monopole type, the resonant modes of the scatterer pair exhibit monopole and dipole properties. By selecting the proper width for the beam, the two resonant modes degenerate, which leads to the total absorption. Although the beam is considerably wide, the frequency range of interest remains below the cut-on frequency of the n = 1 propagating mode, ensuring one-dimensional flexural wave propagation. Further simulations and theoretical analysis revealed that the degeneracy of the monopole and dipole modes results from their interaction with a higher-order localized flexural mode. The simulation results demonstrate absorption exceeding 99%, complemented by experimental data showing approximately 90% absorption.

Honeycomb structure design of automotive crash box

The crash box can protect the safety of passengers when a car collides. Due to its excellent mechanical properties, honeycomb structure can be applied to automotive crash boxes. Two kinds of crash boxes made of regular hexagonal honeycomb structure and re-entrant hexagonal honeycomb are designed. The research results indicate that, compared to the crash box made of hexagonal honeycombs, the crash boxes made of re-entrant hexagonal honeycombs have superior energy absorption ability. Furthermore, the influence of different structural parameters on the energy absorption performance (EAP) of the crash box made of re-entrant hexagonal honeycombs is analyzed. It is found that the total energy absorption and peak force increase with the increase of thickness and concave angle. The research in this article provides certain reference significance for the design of honeycomb structure crash boxes.

Dead Tired

Abstract This essay concerns the descriptions of exhaustion connected to the suicidal thoughts and actions of Anyanwu, the protagonist of Octavia E. Butler’s novel Wild Seed (1980). Expanding the disability studies concept of desirelessness to graze Black diaspora studies, this essay resists the total absorption of enslaved Black women’s suicidal thoughts and actions into the collective political motivations of the living, even as it resists their banishment. Rather than speak authoritatively about an action ultimately undertaken alone, the essay feels for the ordinary edges of the limits of “diaspora” to consider more carefully those who are lost to the collective, those who turn away from it, and those for whom suicide cannot be categorized comfortably as only resistance or defeat. Or, plainly stated: Without purpose and without pity, we can still love you.

Physico-chemical, technological and radiological characteristics of kaolinized granite from northwestern Serbia

In the ceramic industry, the quality of the final ceramic tile as well as the possibility of its use depends on the quality and characteristics of the starting raw materials. One of the potential raw materials that can be used in the production of ceramic tiles is kaolinized granite, and it is necessary to examine its characteristics. In this research, the kaolinized granite of the Jadar block, northwestern Serbia, from the Beli Majdan surface mine, Jadranska Lešnica, was examined. Chemical analysis, X-ray diffraction analysis (XRD), and differential thermal analysis (DTA) were carried out. Ignition tests of the prepared composites were also conducted at three selected temperatures (1000, 1100, and 1250 °C), where total linear shrinkage and water absorption were determined. The activity concentrations of natural radionuclides and the artificial radionuclide 137Cs were determined using the gamma spectrometry method, and then the radiation risk for the external exposure of workers when working with this raw material was assessed. For the samples with the highest content of 226Ra, radon exhalation measurements were performed with the RAD7 device, and the values of the radon emanation coefficient were determined, as well as the values of alpha dose equivalents, which quantified the potential internal exposure of workers. The results of the chemical analysis showed that the content of Al2O3 in the examined composites ranged from 19.11 to 21.00%, and the content of Fe2O3 from 1.53 to 1.72%. Additionally, the K2O content in the tested composites ranges from 4.01 to 5.46%, which indicates the presence of K-feldspar and muscovite, and the Na2O content from 1.82 to 2.61%. Based on XRD analysis, it was established that the mineral composition of kaolinized granite includes quartz, feldspar, mica, calcite/dolomite, and kaolinite minerals. DTA analysis indicates the occurrence of minor endothermic processes at 488.05 °C and 558.12 °C, as well as an exothermic process at 980.8 °C. The color of the ignition is brick red to dark brown red. A trend of increasing linear shrinkage and decreasing water absorption with increasing ignition temperature was observed with the normal appearance of the samples. The average activity concentration of natural radionuclides are around and below the average values for building materials, expect for 40K. The values for 137Cs are below the values measured in soil. Annual effective doses estimated for external exposure are below 1 mSv y−1, which indicates that there is no increased radiation risk when working with this raw material. The values of the radon mass exhalation rate are in the range of 61–113 mBq kg−1 h−1, and the values of the radon emanation coefficient are 6.3–8.4%. The average value of the alpha dose equivalent is 1mSvy−1, which indicates a potential exposure to radon below 100 Bq m−3. Based on the obtained results, it can be concluded that kaolinized granite is a high-quality and radiologically safe raw material for making ceramic composites in the production of ceramic tiles. It has all the necessary characteristics to partially or completely replace feldspar in ceramic composites.

Response of the orthogonal corrugated sandwich panel under low-velocity impact with different shaped impactors

This study aims at investigating the low-velocity impact resistance of the composite orthogonal corrugated sandwich panel through experimental and simulation methods, considering different shaped impactors. To that scope, the progressive damage model with the sandwich panel is developed and numerical investigations are carried out in ABAQUS / Explicit. The results show that as the impactor changes from flat to hemispherical and then to conical shape, the first peak load gradually decreases, and the maximum displacement of the impactor and total energy absorption gradually increase. The high impact energy makes the sandwich panel more compliant. Furthermore, the expansion area of fiber damage, matrix damage and delamination in the top face sheet, core and bottom face sheet depends on the impactor shape and impact energy. Under high impact energy, the damage under the conical impactor mainly expands along the thickness direction of the sandwich panel rather than in the in-plane direction, while the flat impactor causes large damage area in the in-plane direction as well.

Optimization of functionally graded solid-network TPMS meta-biomaterials

The current study enhances the performance of solid-network triply periodic minimal surface (TPMS) cellular materials through using cell size grading along with the Taguchi method. Cell size grading is a novel technique used to control the size of pores and the surface area without changing the relative density. In this context, experimental compression testing was conducted on six distinct geometries of cell size graded TPMS structures (Diamond, Fischer–Koch S, Gyroid, IWP, Primitive, and Schoen–F-RD) manufactured with dental resin using a masked stereolithography (MSLA) printer. The findings indicated that mean total energy absorption was greater for smaller initial cell sizes (4 and 6 mm) compared to larger sizes (12 mm). Consistent patterns were also observed with respect to final cell sizes. Upon examination of the stress-strain relationships between D and I-WP, it is evident that D exhibits a higher initial peak stress point. However, subsequent to a significant decline, it exhibits a tremendous degree of volatility before recovering. Conversely, I-WP demonstrated greater stability throughout the experiments, with a notably greater maximum stress effect. A significant influence was observed from the initial cell size on stress, with larger sizes leading to a reduction in absorbed energy. The acquired results serve as an essential basis for the identification of optimized designs that may be implemented to enhance the structures' durability.

On the Crush Behavior and Energy Absorption of Sustainable Beverage Cans and Their Polyurethane Foam-Filled Structures: An Experimental Study.

In the pursuit of global energy conservation and emissions reductions, utilizing beverage cans as energy-absorbing components offers potential for a sustainable economy. This study examines the impact of foam filling on the crushing behaviors and energy absorption of various types of beverage cans. Quasi-static compression tests were conducted on five geometrically sized cans filled with three densities of polyurethane foam to study their deformation modes and calculate crashworthiness parameters within the effective stroke. Results show that empty beverage cans have lower energy absorption capacities, and deformation modes become less consistent as can size increases. Higher foam density leads to increased total energy absorption, a slight reduction in the effective compression stroke, and a tendency for specific energy absorption to initially increase and then decrease. Regarding crush behavior, smaller cans transition from a diamond mode to a concertina mode, while larger cans exhibit a columnar bending mode. Next, the coupling effect of energy absorption between foam and cans was analyzed so as to reveal the design method of energy-absorbing components. The specific energy absorption of smaller cans filled with polyurethane foam is superior to that of similar empty cans. These findings provide valuable insights for selecting next-generation sustainable energy absorption structures.

Enhanced Electrochemical CO2 Reduction to Formate over Phosphate-Modified In: Water Activation and Active Site Tuning.

Electrochemical CO2 reduction reaction (CO2RR) offers a sustainable strategy for producing fuels and chemicals. However, it suffers from sluggish CO2 activation and slow water dissociation. In this work, we construct a (P-O)δ- modified In catalyst that exhibits high activity and selectivity in electrochemical CO2 reduction to formate. A combination of in situ characterizations and kinetic analyses indicate that (P-O)δ- has a strong interaction with K+(H2O)n, which effectively accelerates water dissociation to provide protons. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) measurements together with density functional theory (DFT) calculations disclose that (P-O)δ- modification leads to a higher valence state of In active site, thus promoting CO2 activation and HCOO* formation, while inhibiting competitive hydrogen evolution reaction (HER). As a result, the (P-O)δ- modified oxide-derived In catalyst exhibits excellent formate selectivity across a broad potential window with a formate Faradaic efficiency as high as 92.1 % at a partial current density of ~200 mA cm-2 and a cathodic potential of -1.2 V vs. RHE in an alkaline electrolyte.

Effects of differential hardening on energy absorption prediction of AA6061-T6 thin-walled rectangular tube

In this study, the energy absorption characteristics and deformation modes of AA6061-T6 thin-walled rectangular tube are investigated experimentally and numerically under different crushing conditions, including axial crushing, three-point bending and oblique crushing. Mechanical tests are carried out on four specimens of uniaxial tension, uniaxial compression, shear and plane strain tension along different loading directions for AA6061-T6. Besides, the effect of differential hardening behavior on the energy absorption prediction of AA6061-T6 rectangular tubes is illustrated by comparing Lou2022, von Mises and SY2009 functions. The mechanical experiment results indicate that AA6061-T6 shows obvious anisotropy, differential hardening behavior and tension-compression asymmetry, and its plastic evolution is accurately characterized by the Lou2022 model. The axial crushing properties show that the AA6061-T6 thin-walled rectangular tube undergoes the progressive symmetrical folding deformation mode. The introduction of geometric discontinuity can obviously reduce the peak force and improve the crashworthiness performances under the axial load. The main crushing mode is bending with a small amount of indentation for three-point bending. Moreover, the three-point bending simulation shows that the Lou2022 function considering differential hardening behavior has the highest simulation accuracy. Three different oblique crushing simulations of 10∘, 20∘ and 30∘ illustrate that the AA6061-T6 rectangular tube at 10∘ mainly occurs progressive folding deformation. while the other two oblique crushing angles undergo global buckling deformation. The total energy absorption at 10∘ is 1.87 and 2.43 times of that at 20∘ and 30∘, respectively. The crushing force efficiency of 20∘ and 30∘ is 41.28 % and 31.8 % lower than that of 10∘, respectively. A comprehensive understanding of the energy absorption performance of AA6061-T6 thin-walled rectangular tube under different crushing conditions is helpful to determine its position and shape as a vehicle safety structure, and to exert its optimal plastic deformation potential to dissipate the collision energy and ensure passenger safety.

Enhancing Electrocatalytic CO2-to-CO Conversion by Weakening CO Binding through Nitrogen Integration in the Metallic Fe Catalyst.

Metallic iron (Fe) typically demonstrates the unfavorable catalytic activity for the CO2 reduction reaction (CO2RR), mainly attributed to the excessively strong binding of CO products on Fe sites. Toward this end, we employed an effective approach involving electronic structure modulation through nitrogen (N) integration to enhance the performance of the CO2RR. Here, an efficient catalyst has been developed, composed of N-doped metallic iron (Fe) nanoparticles encapsulated in a porous N-doped carbon framework. Notably, this N-integrated Fe catalyst displays significantly enhanced performance in the electrocatalytic reduction of CO2, yielding the highest CO Faradaic efficiency of 97.5% with a current density of 6.68 mA cm-2 at -0.7 V versus the reversible hydrogen electrode. The theoretical calculations, combined with the in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy study, reveal that N integration modulates the electron density around Fe, resulting in the weakening of the binding strength between the Fe active sites and *CO intermediates, consequently promoting the desorption of CO and the overall CO2RR process.

Tunability of the nonlinear optical absorption in a GaAs/Ga0.7 Al0.3 As spherical quantum dots under external factors

We theoretically studied the linear, third-order nonlinear and total optical absorption coefficient changes of a typical GaAs/Al0.3Ga0.7As quantum dot system under the influence of hydrostatic pressure and temperature. The influence of hydrostatic pressure and temperature on the system is treated within the framework of effective mass. In this method, the relative changes of linear and nonlinear absorption coefficients are obtained by using density matrix method and iterative method. In addition, we also reveal the mechanism of the influence of hydrostatic pressure and temperature on the nonlinear optical properties, which is of great significance for us to better understand the causes. We have shown that hydrostatic pressure and temperature change the effective mass, resulting in significant changes in the linear and nonlinear optical properties of the system. In addition, we also reveal the mechanism of the influence of effective mass on the nonlinear optical properties, which is of great significance for us to better understand the causes.

12C6+ Irradiation Mutation for the Selection and Breeding of High-Cholesterol-Lowering Lactobacillus

A high-throughput screening method for the selection of lactic acid bacteria with high cholesterol-degrading ability was established using the 12C6+ beam irradiation mutagenesis technique. This study aimed to breed excellent strains with high cholesterol-degrading capability and explore the mechanisms of cholesterol degradation by these strains. The mutated strains JMR-01 (Lactobacillus reuteri) and SN-2 (Lactobacillus rhamnosus) after irradiation were primarily screened for high cholesterol-degrading strains by optimizing the KENJI culture medium with colony diameter as an indicator. The primary screened strains were further screened using ammonium ferric sulfate method. The mechanisms of cholesterol degradation by lactic acid bacteria were further investigated by determining the total cholesterol degradation rate, the cholesterol degradation rate through co-precipitation and absorption. The results showed that after primary and secondary screening, four mutant strains with high cholesterol-degrading ability (JMR-01-1, JMR-01-2, SN-2-1, SN-2-9) were selected. The cholesterol-degrading ability of strain JMR-01-1 was increased by 9.7% compared to the original strain JMR-01 (P<0.05), and the cholesterol-degrading ability of strain SN-2-1 was increased by 11.5% compared to the original strain SN-2. The total cholesterol degradation rate, co-precipitation, and absorption of cholesterol degradation rate of the four mutant strains showed no significant difference in the co-precipitation effect on cholesterol compared to the original strains, but the relative absorption rate was significantly increased. This study optimized the screening method for cholesterol-degrading strains and demonstrated through the exploration of different cholesterol degradation pathways by lactic acid bacteria that this screening method can select strains with high cholesterol absorption capacity.

ДЕКОМПОЗИЦИЯ СПЕКТРА ПОГЛОЩЕНИЯ АЦЕТОНОВОГО ЭКСТРАКТА МИКРОВОДОРОСЛИ ARTHROSPIRA (SPIRULINA) PLATENSIS NORTH. GEITL.

We have described the absorption spectra of acetone extract of the microalga Arthrospira (Spirulina) platensis by mathematical models of carotenoids and chlorophylls in the range from 400 to 700 nm. The obtained values of pigment concentrations agree well with standard methods. A model of the absorption spectrum of acetone extract of A. platensis can be used to determine the concentration of chlorophyll a and carotenoids. The absence of chlorophyll b contribution to the total absorption spectrum was shown. The method of mathematical separation of acetone extract absorption spectrum in Microsoft Excel program was implemented. Calculations performing approximations of pigment concentrations by minimizing the sum of squares of deviations between the true absorption spectrum and its mathematical model have been performed using the spreadsheet processor with the help of the solution search tool.