Oxide Chains Research Articles

Inhibiting Effect of 4-Hydroxy-2,5-Dimethylfuran-3-one on the Radical Chain Oxidation of Styrene

The O–H bond strength was calculated by the G4 and the M06-2X/MG3S methods for 2‑hydroxy-3-methylcyclopent-2-en-1-one (maple lactone), 4-hydroxy-2,3-dimethyl-2H-furan-5-one (sotolon), 4-hydroxy-5-methylfuran-3-one, 4-hydroxy-2,5-dimethylfuran-3-one (strawberry furanone), (2R)-2-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxy-2H-furan-5-one (ascorbic acid), 5-hydroxy-2-(hydroxymethyl)pyran-4-one (kojic acid), 3-hydroxy-2-methylpyran-4-one (maltol), 3-hydroxy-2-ethylpyran-4-one (ethylmaltol), 4-hydroxy-6-methylpyran-2-one, and 5-hydroxy-6-methyl-3,4-dihydro-2H-pyran-4-one (dihydromaltol). The calculations indicated the presence of a weak O–H bond of less than 82.0 kcal/mol in 4-hydroxyfuran-3-one derivatives. The experimental rate constant of the reaction of the compound with the lowest O–H bond strength, 4-hydroxy-2,5-dimethylfuran-3-one, with peroxyl radicals in chlorobenzene and acetonitrile was comparable to the data for dibutylhydroxytoluene, but the stoichiometric coefficient of inhibition was 0.17 (PhCl) and 0.66 (MeCN), which was significantly smaller than for dibutylhydroxytoluene. The activation enthalpy for hydrogen atom elimination from 4-hydroxy-2,5-dimethylfuran-3-one by peroxyl radicals calculated by the SMD(PhCl)-M05/MG3S method correlated well with the data for 5-hydroxy and 5-aminouracil derivatives, which is indicative of the common mechanism of interaction of these compounds with peroxyl radicals.

Improved CO2/CH4 separation performance of mixed‐matrix membrane by adding ZIF‐7‐NH2 nanocrystals

AbstractMembrane‐based technology is an attractive alternative in terms of CO2 separation. Pebax‐based membranes are regarded as potential candidates for CO2 separation due to the favorable interaction between its poly (ethylene oxide) chains with CO2 molecules and inorganic fillers. However, the separation performance for CO2/CH4 mixture is still suffered from the moderate gas permeability and selectivity. To overcome this problem, in this work, amino‐functionalized zeolite imidazolate framework (ZIF‐7‐NH2) nanocrystals were used as fillers to blend with Pebax 1657 for fabricating mixed‐matrix membranes (MMMs). XRD, Brunauer–Emmett–Teller (BET), scanning electron microscope, and 1H nuclear magnetic resonance characterization indicated that ZIF‐7‐NH2 with the highest crystallinity was synthesized. Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and Young's modulus showed that it has good interfacial interaction. Gas separation test results showed that both the CO2 permeability and CO2/CH4 selectivity of the 31 wt% ZIF‐7‐NH2/Pebax MMMs increased by 80 and 170%, respectively. The improved performance is attributed to the addition of ZIF‐7‐NH2 nanocrystals and the favorable interfacial interactions between the polymer and ZIF‐7‐NH2 nanocrystals. Furthermore, the polyvinylidene fluoride supported hollow fiber composite membranes also exhibit the long‐term stability for CO2/CH4 separation.

Free radical detection in water after processing by means of high voltage electrical discharges and high power ultrasound

Nonthermal processing technologies have been researched in lab scale for more than 15 years. In this study, the influence of sonification and high voltage electrical discharge—plasma treatment of water on the formation and stabilization of hydroxyl radicals has been investigated by electron paramagnetic resonance (EPR) spectroscopy and spin-trapping method. As analysis tool, an agglomerative hierarchical clustering was used in grouping samples recorded by EPR and near infrared spectroscopy (NIR) spectroscopy. Also, the multivariate analysis was performed using the principal component analysis (PCA) and Principal Regression models (PCR). Results for ultrasound-treated samples showed that number of radicals is increasing with treatment time and increase in amplitude. High-voltage electrical discharge treatment at 120 Hz resulted in the formation of the largest number of hydroxyl radicals. Developed PCR models are highly effective in prediction of NIR spectra, regardless the sample treatment what is an additional step forward in green technology. Practical applications Usage of electron paramagnetic resonance measurement can be used in laboratory and scale-up treatments by nonthermal processing. It is of outmost importance to monitor the production of free radicals, from starting of processing, in order to avoid overtreatment of foods and to avoid possible oxidation and unwanted radical chain reactions. Monitoring of processing can be used to optimize nonthermal processing and to avoid production of unwanted oxidative products and compounds.

Aqueous phase behavior of the PEO-containing non-ionic surfactant C12E6: A molecular dynamics simulation study

HypothesisNon-ionic surfactants containing polyethylene oxide (PEO) chains are widely used in drug formulations, cosmetics, paints, textiles and detergents. High quality molecular dynamics models for PEO surfactants can give us detailed, atomic-scale information about the behavior of surfactant/water mixtures. SimulationsWe used two molecular dynamics force fields (FFs), 2016H66 and 53A6DBW, to model the simple non-ionic PEO surfactant, hexaoxyethylene dodecyl ether (C12E6). We investigated surfactant/water mixtures that span the phase diagram of starting from randomly distributed arrangements. In some cases, we also started with prebuilt, approximate models. The simulations results were compared with the experimentally observed phase behavior. FindingsOverall, this study shows that the spontaneous self-assembly of PEO non-ionic surfactants into different colloidal structures can be accurately modeled with MD simulations using the 2016H66 FF although transitions to well-formed hexagonal phase are slow. Of the two FFs investigated, the 2016H66 FF better reproduces the experimental phase behavior across all regions of the C12E6/water phase diagram.

Monitoring chemical synthesis of human atrial natriuretic peptide by ultra high performance liquid chromatography-mass spectrometry analysis

Peptides participate in and regulate many important life processes as neurotransmitters, hormones and receptors. With detailed understanding of the structure and function of peptides, chemically synthesized peptides have shown great value in the fields of biomedicine and life analysis. Human atrial natriuretic peptide (ANP) is a polypeptide hormone consisting of 28 amino acids. The abnormalities in the content and metabolism of ANP are closely related to the diseases like cardiovascular diseases and cancer. In view of the important physiological functions of ANP, herein we monitored and optimized the chemical synthesis of ANP chemical synthesis. The strategy involved integrating solid phase synthesis of linear peptide chain and liquid phase oxidation. Based on the excellent separation performance of HPLC and the excellent qualitative ability of mass spectrometry (MS), a new method based on ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was established to monitor the synthesis reaction and to separate and purify the obtained products. This study provides a reference for the efficient chemical synthesis and oxidative ring formation of human atrial natriuretic peptide.

Biodegradation of typical azole fungicides in activated sludge under aerobic conditions

Widespread use of azole fungicides and low removal efficiency in wastewater treatment plants (WWTPs) have led to the elevated concentration of azole fungicides in receiving environment. However, there was limited research about the removal mechanism of azole fungicides in the biological treatment of WWTPs. Imidazole fungicide climbazole and triazole fungicide fluconazole were selected to investigate the biodegradation mechanism of azole fungicides in activated sludge under aerobic conditions. Climbazole was found to be adsorbed to solid sludge and resulted in quick biodegradation. The degradation of climbazole in the aerobic activated sludge system was fitted well by the first-order kinetic model with a half-life of 5.3 days, while fluconazole tended to stay in liquid and had only about 30% of loss within 77 days incubation. Ten biotransformation products of climbazole were identified by high resolution mass spectrometry using suspect and non-target screening method. But no biodegradation products of fluconazole were identified due to its limited removal. The possible biodegradation pathways for climbazole were proposed based on the products identification and pathway prediction system, and involves oxidative dehalogenation, side chain oxidation and azole ring loss. The findings from this study suggest that it should be a concern for the persistence of fluconazole in the environment.

Synthesis and study of the gas sensitive properties of composite thin films of copper oxide and linear chain carbon

The possibility of synthesizing semiconductor films of copper oxide and films of copper oxide with linear chain carbon, which have good sensitivity to methanol and ethanol vapors, is shown in the work by a thermoresistive method. The proposed gas sensitivity mechanism describing the increase in resistance in methanol and ethanol vapors shows good agreement with the obtained experimental results.

Ageing Assessment of XLPE Cable Insulation by Residual Antioxidant Content

To improve the efficiency and accuracy of cable ageing assessment, a new method based on residual antioxidant (AO) content is proposed. Cross-linked polyethylene (XLPE) cable insulation is thermally aged in laboratory at 110, 130 and 140°C from 240 h to 3600 h. The ageing degree of XLPE is characterized by tensile testing, AC breakdown measurement, and Fourier transform infrared spectroscopy. The residual AO content in XLPE is detected by FTIR as well as by oxidation induction time (OIT) measurement. It is observed that residual AO content measured by FTIR decreases monotonously with ageing time while OIT shows a non-monotonic transition. The results demonstrate that thermal deterioration is closely related to residual AO content and a critical value of residual AO content exists. During early stage of thermal ageing, the residual AO content is larger than the critical value and the variation in XLPE properties is relatively small. When the residual AO content decreases below the critical value, significant deterioration occurs. The close relationship between thermal degradation and residual AO content was analyzed by oxidative chain reactions.

Study of reduction of antioxidant protection in the pathogenesis of experimental diabetic retinopathy

The prevalence of diabetes mellitus (DM) is growing among the population of countries of the world, depending on the region, the level of economic development of the country, gender and age. The antioxidant system plays an important role in protecting the cells of the body from permanent and numerous damage that occurs due to the pathological influence of free radicals. Antioxidant enzymes, and peroxidases in particular, block the initiation of chain oxidation processes, preventing, among other things, the processes of DNA damage by free radicals that provoke the process of mutagenesis.Our results indicate the development of oxidative stress in the pathogenesis of experimental diabetic retinopathy, as evidenced by a pronounced decrease in the activity of the antioxidant defense enzyme under the conditions of our study.Already on the thirtieth day of the development of experimental diabetic retinopathy, a decrease in peroxidase activity was observed, followed by the progression of pathological changes on the sixtieth day of the study.The most pronounced decrease in the activity of the studied marker of antioxidant defense was found at the 3rd stage of the experiment.

Coenzyme Q10 enhances remyelination and regulate inflammation effects of cuprizone in corpus callosum of chronic model of multiple sclerosis.

Multiple Sclerosis (MS) is a chronic, progressive demyelinating disease of the central nervous system that causes the most disability in young people, besides trauma. Coenzyme Q10 (CoQ10)-also known as ubiquinone-is an endogenous lipid-soluble antioxidant in the mitochondrial oxidative respiratory chain which can reduce oxidative stress and inflammation, the processes associated with demyelination in MS. Cuprizone (CPZ) intoxication is a well-established model of inducing MS, best for studying demyelination-remyelination. In this study, we examined for the first time the role of CoQ10 in preventing demyelination and induction of remyelination in the chronic CPZ model of MS. 40 male mice were divided into four groups. 3 group chewed CPZ-containing food for 12weeks to induce MS. After 4weeks, one group were treated with CoQ10 (150mg/kg/day) by daily gavage until the end of the experiment, while CPZ poisoning continued. At the end of 12weeks, tail suspension test (TST) and open field test (OFT) was taken and animals were sacrificed to assess myelin basic protein (MBP), oligodendrocyte transcription factor-1 (Olig1), tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) by real-time polymerase chain reaction (real-time PCR) and total antioxidant capacity (TAC) and superoxide dismutase (SOD) by Elisa test. Luxol fast blue (LFB) staining was used to evaluate histological changes. CoQ10 administration promoted remyelination in histological findings. MBP and Olig-1 expression were increased significantly in CoQ10 treated group compare to the CPZ-intoxicated group. CoQ10 treatment alleviated stress oxidative status induced by CPZ and dramatically suppress inflammatory biomarkers. CPZ ingestion made no significant difference between normal control group and the CPZ-intoxicated group in TST and OFT. CoQ10 can enhance remyelination in the CPZ model and potentially might have same effects in MS patients.

Evaluation of cellulose paper degradation irradiated by an electron beam for conservation treatment

In this study, we investigate the chemical, physical and optical properties of cellulose paper irradiated by an electron beam for disinfection. Cellulose chain scission and oxidation induced by radiation increased considerably at 25 kGy irradiation, whereas folding endurance, morphology, and crystallinity did not undergo significant changes. The cellulose chain scission rate of paper irradiated under air-dried and wet conditions showed no difference; however, cellulose oxidation increased to a higher degree in paper irradiated under wet conditions than under air-dried conditions. Electron beam irradiation did not significantly affect changes in paper color, which is associated with oxidation. However, when irradiated papers were aged, the color difference increased according to the irradiation dose, as the oxidized functional groups of cellulose can act as a trigger for color change. A linear relationship between the cellulose chain scission rate and irradiation dose was found; thus, the cellulose chain scission rate can be predicted for a specific dose. The degree of polymerization was calculated from the predicted cellulose chain scission rate using the Ekenstam equation. According to the prediction, the degree of polymerization decreased to 74% at a dose of 5 kGy, a suitable dose for paper disinfection. In the low-dose range, electron beam irradiation did not adversely affect the physical properties of paper, but significant changes occurred in both the chemical and optical properties of paper. Thus, electron beam irradiation may be of use in disinfecting severely degraded paper due to biological factors; however, the irradiation process diminishes paper permanence.

Electrolysis-sulfate-reducing up-flow sludge bed-biological contact oxidation reactor for Norfloxacin removal from wastewater with high sulfate content

This study investigated the treatment of 100-mg/L Norfloxacin (NOR) wastewater containing high concentrations of sulfate through a combination of electrolysis, sulfate-reducing up-flow sludge bed (SRUSB), and biological contact oxidation reactor (BCOR) treatments. Results revealed that after 62 h, the reaction system had processed over 97% of the NOR. Additionally, electrolysis with sodium sulfate as the electrolyte transformed 87.8% of the NOR but only 33.5% of the total organic carbon (TOC). In the SRUSB, the TOC and SO42− contents were simultaneously reduced by 87.4% and 95.6%, respectively, providing a stable environment to the BCOR. In the BCOR, 36.3% and 85.9% of the NOR and TOC were degraded. High-performance liquid chromatography-tandem mass spectrometry analysis identified three possible degradation pathways under the attack of –OH during electrolysis, including defluorination, piperazinyl ring transformation, and quinolone ring transformation. Furthermore, the Illumina HiSeq sequencing results demonstrated that the sulfate-reducing bacteria (represented by Desulfobacter and Desulfobulbus) in the SRUSB and the sulfate-oxidizing bacteria (mainly consisting of Gammaproteobacteria and Alphaproteobacteria) in the BCOR played important roles in carbon chain oxidation and benzene ring opening and thoroughly degraded the electrolysis products. Thus, this method effectively overcomes the incomplete degradation and low removal efficiency issues associated with single electrolysis or biological methods in traditional processes.

Experimental study of hypoxia-induced changes in gene expression in an Asian pika, Ochotona dauurica.

Acclimation to environmental changes driven by alterations in gene expression will serve as an important response for some species facing rapid Anthropogenic climate change. Pikas, genus Ochotona, are particularly vulnerable to climate change and current trends suggest that only the highest, coldest elevations within their ranges may remain suitable habitat for these species. In this study we aimed to assess the role of changes in gene expression in potentially facilitating elevational movements in pikas by measuring gene expression in the only known captive pika population, Ochotona dauurica, in response to hypoxic conditions. Using a controlled experiment, we exposed four male pikas to oxygen concentrations characteristic of sea-level, 2,000 m, and 4,000 m for 5 days each. Using blood samples collected after each treatment, we used RNAseq to determine if candidate pathways were undergoing significant changes in gene expression at different levels of oxygen (~100%, ~77%, and ~61% of sea-level oxygen concentrations). Gene set enrichment analyses showed that gene sets associated with the oxidative phosphorylation pathway and electron transport chain were significantly enriched for up-regulated genes in the 4,000 m samples compared to samples from the same individuals at lower-elevation conditions. Up-regulation of these pathways is consistent with known mechanisms of oxygen compensation. Our results suggest that these pikas have the acclimation capacity to tolerate oxygen concentrations characteristic of any elevation within their species range and that gene expression can be changed in a matter of days to accommodate drastically different oxygen concentrations. Thus, rapid and radical elevational movements that may be required of some pika species to avoid warmer temperatures in the Anthropocene will likely not be limited by hypoxic stress.

Cardiolipin in Immune Signaling and Cell Death.

Cardiolipin (CL) is a tetra-acylated diphosphatidylglycerol lipid. In physiological conditions, CL presents unsaturated chains and is located in the inner mitochondria membrane (IMM). Dead signals, infection, or disease may change the level of CL saturation and oxidation and cause its translocation to the cytosolic side of the outer mitochondrial membrane (OMM), affecting mitochondrial function and the inflammatory response. In this review, we summarize the emerging proapoptotic, pro-, and anti-inflammatory functions of cytosolic-exposed CL and how they are regulated by CL chain saturation and oxidation. We underline how the unique dimeric phospholipid structure confers peculiar properties on CL in the regulation of cell death and immune system proteins, such as the Nucleotide-binding domain and leucine-rich repeat-containing pyrin protein 3 (NLRP3), caspases (Casp), and Toll-like receptor 4 (TLR4). We also provide an overview of the human diseases in which CL deficiency or modification are implicated and of the use of exogenous unsaturated CL (uCL) as a novel therapeutic approach.

Wettability effect of ethoxylated nonyl phenol with different ethylene oxide chain length on Shendong long-flame coal surface

Low-rank coal is coal with a low degree of metamorphism, it has high moisture content and strong hydrophilicity. It is important for low rank coal to improve its hydrophobicity. In this paper, the wettability effects of ethoxylated nonylphenol (NPEO) with different ethylene oxide chain length on Shendong long-flame coal surface were explored. Contact angle experiments proved that long-flame coal adsorbing NPEO significantly enhances its surface hydrophobicity, and it is the most effective when the equilibrium concentration is close to its critical micelle concentration. Moreover, NPEO-8 is the best for improving the hydrophobicity of long-flame coal. Compared with long-flame coal without NPEO, the surface energy and adhesion work of coal are lower after adsorbing NPEO, in addition, NPEO-8 is the most effective of three NPEO with 8, 10 and 12 ethylene oxide. NPEO aggregate at the coal/water interface and the hydrophobic carbon chains intertwine to form a hemispherical aggregate structure, which reduce the interaction energy between water and coal. Therefore, the hydrophobicity of long-flame coal was improved after adsorbing NPEO, and NPEO-8 is the best, followed by NPEO-10, NPEO-12 is the last.

Crosslinked PPO-based anion exchange membranes: The effect of crystallinity versus hydrophilicity by oxygen-containing crosslinker chain length

Crosslinked poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) using hydrophilic crosslinkers that contain ethylene oxide (EO) were prepared as novel anion exchange membranes (AEMs), and the effect of crosslinker EO length was systematically investigated. The physicochemical, morphological and electrochemical properties of the corresponding AEMs were also compared against the membrane prepared from a typical hydrophobic alkyl-type crosslinker. The ethylene oxide crosslinker helped to form ion clusters and to enhance the water-holding capacity of the corresponding AEMs, which promoted high conductivity both in water and in 95% room humidity conditions, whilst maintaining high physicochemical stability. However, it was also found that the presence of a long ethylene oxide as a crosslinker may induce polymer crystallinity, which reduces both conductivity and the alkaline stability of the corresponding crosslinked membranes. The effect of ethylene oxide chain length on the morphology, electrochemical and physicochemical properties, were also investigated. The xBEO-PPO membrane, having bis(ethylene oxide) (BEO) as a crosslinker, showed the highest conductivity of 131.96 mS/cm in water at 80 °C, and 55.21 mS/cm in 95% RH at 80 °C; this was owing to its crystalline nature. The single-cell performance of 444 mW/cm2 peak power density, was also obtained from the xBEO-PPO membrane.

RADIOPROTECTIVE PROPERTIES OF POLYPHENOLIC COMPOUNDS OF EDIBLE AND AROMATIC PLANTS

The proliferation of nuclear technologies threatens by the negative impact of ionizing radiation on the human body and requires the search of new effective means for prevention from radiation damage. Informational search in scientific editions and search databases on radioprotective effects of food and aromatic plants, radiation nephropathy and promising herbal drugs for its prevention has been carried out. Methods of analysis, systematization, comparison, generalization of information data have been applied. An overview of the results of experimental phytochemical and clinical studies of domestic and foreign scientists on radioprotective effects of biologically active substances of food and aromatic herbs has been carried out. It is revealed that plant polyphenolic compounds, due to their antioxidant properties, are able to neutralize free radicals and thus leading to a stop of radio-induced chain oxidation reactions in cells, to scavenge and neutralize of lipoperoxyl radicals, chelate ions of metals, as well as to exhibit antimutagenic activity. Radiotherapy might cause several radiation-induced kidney injuries, including radiation nephropathy. Search of promising herbal substances for prevention and alleviation of radiation nephropathy is under active investigation in recent years. Preventive inclusion of radioprotective agents, containing polyphenolic compounds, before irradiation seems to be an obvious renoprotective strategy. The prospect for further phytochemical, pharmacodynamic and toxicological studies of properties of polyphenolic compounds in food and aromatic plants with an objective to create new effective remedies for the prevention and treatment of radiation damage is shown.

Synthesis, Characterization and Magnetic Hyperthermia of Monodispersed Cobalt Ferrite Nanoparticles for Cancer Therapeutics.

Magnetic nanoparticles such as cobalt ferrite are investigated under clinical hyperthermia conditions for the treatment of cancer. Cobalt ferrite nanoparticles (CFNPs) synthesized by the thermal decomposition method, using nonionic surfactant Triton-X100, possess hydrophilic polyethylene oxide chains acting as reducing agents for the cobalt and iron precursors. The monodispersed nanoparticles were of 10 nm size, as confirmed by high-resolution transmission electron microscopy (HR-TEM). The X-ray diffraction patterns of CFNPs prove the existence of cubic spinel cobalt ferrites. Cs-corrected scanning transmission electron microscopy–high-angle annular dark-field imaging (STEM–HAADF) of CFNPs confirmed their multi-twinned crystallinity due to the presence of atomic columns and defects in the nanostructure. Magnetic measurements proved that the CFNPs possess reduced remnant magnetization (MR/MS) (0.86), which justifies cubic anisotropy in the system. Microwave-based hyperthermia studies performed at 2.45 GHz under clinical conditions in physiological saline increased the temperature of the CFNP samples due to the transformation of radiation energy to heat. The specific absorption rate of CFNPs in physiological saline was 68.28 W/g. Furthermore, when triple-negative breast cancer cells (TNBC) in the presence of increasing CFNP concentration (5 mg/mL to 40 mg/mL) were exposed to microwaves, the cell cytotoxicity was enhanced compared to CFNPs alone.

Reactivity and mechanism of action of selenochromenes used as an inhibitor for the radical chain oxidation of 1,4-dioxane

Organometallic compounds based on selenochromene are known as potential drugs. Currently in the creation of new drugs in pharmacology their role as antioxidants is given great importance, since this characteristic is important for inhibiting the possible radical chain oxidation processes of cell membrane lipids, which is the cause of much pathology. In this regard an important task of researchers is to study the mechanism and quantitative characteristics of the effectiveness of their antioxidative action. In this work, based on the previously studied kinetics of the antioxidant action of the additives 2-(4-biphenyl)-5,6-dihydro-4H-benzo-[h]-selenochromene (S1) and 2-(4-chlorophenyl)-4-phenyl-5,6-dihydro-4H-benzo-[h]-selenochromene (S2) in a model reaction of radical-chain oxidation of 1,4-dioxane (Khairullina et al. in Kinet Catal 54:14–17, 2013), by means of mathematical modeling a kinetic model of the process was constructed, with the help of which the analysis of the reaction mechanism was carried out, a complete kinetic picture of the process was obtained and stage rate constants.

High-Frequency Heating of a Multiply Protonated Poly(ethylene oxide) Chain in a Vacuum

Heating of a multiply protonated poly(ethylene oxide) chain in an intense high-frequency electric field in a vacuum is studied using molecular dynamics simulations. The rate of absorption of the field energy by the chain is determined at the field frequencies from 0.5 to 150 GHz. The absorption spectrum depends on the number of attached protons n, and also on the temperature of the chain. At low n and high temperatures, the spectrum consists of several distinct peaks with the most intense peak at a frequency of about 10 GHz. When n is large, the peaks are less pronounced and the energy absorption rate reaches a maximum at the lowest studied frequency.The effect of n on the energy absorption rate depends on the field frequency. While at low and high frequencies the energy absorption rate increases almost in proportion to n, near the main absorption peak it decreases.This indicates that there are two different mechanisms of the energy absorption. Firstly, the chain absorbs energy during resonant vibrations that occur at several frequencies. Secondly, the chain absorbs energy through a process that occurs over a wide frequency range and becomes more intense with decreasing frequency.