Peak Intensity Research Articles

Application of Raman spectroscopy for analyzing the behavior of gases in sandstone reservoirs

The behavior of gases within subsurface pores determines the oil and gas recovery and CO2 storage in the region. In this study, we report a novel method based on Raman spectroscopy for observing the distributions of CH4 and CO2 gases in the pores of sandstone reservoirs. First, we designed a pressure-cell to inject gases into a sample. Then, CH4 and CO2 gases were injected into the sample using the pressure-cell placed on the Raman spectroscopy system sample stage. Quartz and feldspar were the predominant minerals in the sample. The CH4-occupied pores exhibited a Raman peak at 2917 cm−1. Two-dimensional (2D) and three-dimensional (3D) mapping of the pores depicted the geometry of the CH4 gas-filled pores. After injecting CO2 gas, we observed an intensity peak at 1388 cm-1; we obtained 2D and 3D maps of the CO2 gas-filled pores based on this peak value. This study demonstrates the potential use of Raman spectroscopy as a visualization tool to reveal the pore geometry of sandstone reservoirs and determine the distribution of gases within such reservoirs. Our study can serve as a foundation for understanding the behavior of gases in subsurface reservoirs, improving oil and gas prospecting and exploration, and assessing CO2 storage..

Plant-Mediated Synthesis of Zinc Oxide (ZnO) Nanoparticles Using Alnus nepalensis D. Don for Biological Applications

An aqueous bark extract of A. nepalensis D. Don was utilized to prepare zinc oxide (ZnO) nanoparticles through a green method, which is more economical, eco-friendly, and effective for exploring several biological applications and toxicity assessments against brine shrimp nauplii. The prepared ZnO nanoparticles were characterized using several characterizing techniques. The surface morphology and the elemental composition of the prepared ZnO NPs was analyzed by field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray (EDX) analysis. The colour of the solution was changed from reddish-brown to white indicating the formation of ZnO NPs which shows UV-vis absorption at 361 nm. The various functional groups of the organic compounds present in plant extract act as reducing and stabilizing agents in the formation of nanoparticles. The involvement of these functionalities in the formation of nanoparticles is indicated by the shifts and changes in the IR spectra of both the plant extract and the ZnO nanoparticles. The size of the nanoparticles was determined to be 15.31 nm with XRD analysis while the FE-SEM revealed the average grain size of 67.29 nm with irregular shape. The elemental composition of ZnO NPs shows a greater atomic percentage of zinc compared to other elements (C, N, Ni, O, and Ag), with an intense peak of zinc observed at approximately 1 keV. The trace amount of silver is due to the impurities present in the reagent used in the experiment. The antioxidant property of ZnO nanoparticles was evaluated with an IC₅₀ of 53.02 ± 3.43 μg/mL. The ZnO nanoparticles exhibited significant antibacterial activity against Klebsiella pneumoniae and Escherichia coli, with zones of inhibition (ZOI) of 18 mm and 23 mm, respectively as compared to the positive control neomycin of ZOI 28 mm against K. pneumoniae. The potential antibacterial activity of the ZnO NPS was revealed as the MIC and MBC against K. pneumoniae of 0.39 mg/mL and 0.78 mg/mL, respectively. In addition, the prepared ZnO nanoparticles showed toxicity against brine shrimp nauplii of LC₅₀ 16.59 μg/mL. The results of this study impart that plant-assisted synthesized ZnO nanoparticles possess significant antibacterial properties that reduce oxidative stress in human cells, ultimately contributing to cancer prevention.

Karakteristik Sensori dan Fisikokimia Kukis dari Campuran Tepung Mocaf dan Tepung Kulit Buah Naga

To support the goal of zero waste outlined in the sustainable development goals (SDGs), repurposing dragon fruit peel waste presents a promising opportunity. In Indonesia, the high demand for dragon fruit leads to the generation of considerable organic waste. This study explored the use of dragon fruit peel flour, combined with modified cassava (mocaf) flour, as a wheat flour alternative to improve the sensory and chemical properties of gluten-free cookies. The research involved preparing the flours and cookies, followed by conducting sensory, physical, and chemical analyses. A completely randomized design (CRD) was employed, testing five formulations with varying ratios of mocaf flour to dragon fruit peel flour. The results indicated that 73% of panelists preferred the crispiness of cookies containing 25% dragon fruit peel flour, while 60% were satisfied with the color of cookies containing 45% dragon fruit peel flour. Physical analysis showed no significant differences in thickness or bake loss, but there were notable differences in diameter, spread ratio, and color. As the proportion of dragon fruit peel flour increased, the cookies showed significant improvements in chemical characteristics, including higher levels of moisture, ash, fat, protein, and fiber content. Additionally, the content of total phenolics and antioxidant activity increased with higher ratios of dragon fruit peel flour, reaching 1.14 mg GAE/g for total phenolics and 662.64 mg AAE/g for antioxidant activity. FTIR analysis revealed a consistent absorbance pattern across samples, with minor variations in peak intensities at specific wavenumbers. Based on the sensory, physical, and chemical evaluations, cookies containing 45% dragon fruit peel flour were recommended for production.

Investigating the impact of shear and bulk viscosity on the damping of confined acoustic modes in phononic crystal sensors

Phononic crystal (PnC) sensors are recognized for their capability to control acoustic wave propagation through periodic structures, presenting considerable potential across various applications. Despite advancements, the effects of fluid viscosity on PnC performance remain intricate and inadequately understood. This study theoretically investigates the influence of shear (dynamic) and bulk viscosity on acoustic wave damping in defective one-dimensional phononic crystal (1D PnC) sensors designed for detecting liquid analytes. Acetic acid with varying viscosities is considered to fill a cavity layer intermediated by a multilayer stack of lead and epoxy. The effects of dynamic and bulk viscosity on the resonance characteristics of the defective mode were analyzed. Numerical results reveal that increased dynamic viscosity leads to substantial broadening and decreased intensity of resonance peaks, accompanied by a shift to higher frequencies due to enhanced elastic wave attenuation and damping. At low dynamic viscosity (η = 0.2 ηd), numerous resonance peaks with varying intensities are observed. However, at higher viscosities (η = 2.0 ηd to η = 10.0 ηd), only one prominent peak appears in the spectrum. The intensity of this resonant peak starts at 98% for η = 2 ηd and decreases to 58.8% as the dynamic viscosity increases to η = 10 ηd. Additionally, the combined effect of dynamic and bulk viscosity introduces further damping, causing a strong shift of the resonance peak to higher frequencies, along with an increase in the full width at half maximum (FWHM) and a decrease in the quality factor (QF). These findings emphasize the necessity of incorporating both shear and bulk viscosity in the design of PnC sensors to enhance their sensitivity and accuracy in practical applications. This theoretical framework provides critical insights for optimizing sensor performance and bridging gaps between theoretical predictions and experimental observations, especially in 1D PnCs, offering potential solutions to challenges in real-world PnC sensor applications.

Non-thermal atmospheric jet plasma effects on the morphological, electrical and optical properties of nanocrystalline silicon

In this study, a non-thermal atmospheric argon plasma jet (NTAPJ) was designed and used to treat the porous silicon layer, prepared by photoelectrochemical etching (PECE). The porous silicon layers were distinguished before and after the cold plasma treatment utilized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), photoluminescence (PL), and dark and photo current-voltage characteristics. The results confirmed the nanostructure of the formed porous silicon. After the treatment with argon plasma, the intensity of the XRD peak increased, and the porosity decreased from 93% to 62%. Additionally, porous silicon's average roughness (Sa) and root mean square (Sq) were reduced from 60.10 to 12.31nm and 73.70 to 16.53nm, respectively. The current-voltage characteristic indicated the increase in photocurrent and the ideality factor, as well as a decrease in dynamic resistance. The photoluminescence results showed a change in PL peaks, represented by a blue shift, an increase in intensity, and a vanishing of another peak.

Investigating the impact of climatic and environmental factors on HFRS prevalence in Anhui Province, China, using satellite and reanalysis data.

Hemorrhagic Fever with Renal Syndrome (HFRS) is the most commonly diagnosed zoonosis in Asia. Despite taking various preventive measures, HFRS remains prevalent across multiple regions in China. This study aims to investigate the impact of climatic and environmental factors on the prevalence of HFRS in Anhui Province, China, utilizing satellite and reanalysis data. We collect monthly HFRS data from Anhui Province spanning 2005 to 2019 and integrated MODIS satellite datasets and ERA5 reanalysis data, including variables such as precipitation, temperature, humidity, solar radiation, aerosol optical depth (AOD), and Normalized Difference Vegetation Index (NDVI). Continuous wavelet transform, Spearman correlation analysis, and Poisson regression analysis are employed to assess the association between climatic and environmental factors and HFRS cases. Our findings reveal that HFRS cases predominantly occur during the spring and winter seasons, with the highest peak intensity observed in a 9-year cycle. Notably, the monthly average relative humidity exhibits a Spearman correlation coefficient of 0.404 at a 4-month lag, taking precedence over other contributing factors. Poisson regression analysis elucidates that NDVI at a 2-month lag, mean temperature (T) and solar radiation (SR) at a 4-month lag, precipitation (P), relative humidity (RH), and AOD at a 5-month lag exhibit the most robust explanatory power for HFRS occurrence. Moreover, the developed predictive model exhibiting commendable accuracy. This study provides key evidence for understanding how climatic and environmental factors influence the transmission of HFRS at the provincial scale. Insights from this research are critical for formulating effective preventive strategies and serving as a resource for HFRS prevention and control efforts.

Nanoscale Synergy: Unveiling Gas Sensing Paradigms Through First Principles Exploration of Vertical Hexagonal Boron Nitride/Graphene Heterostructures

Modern civilization relies on rapid and accurate gas molecule identification at low concentrations for environmental surveillance, civilian security, healthcare evaluation, and inside atmospheric control. Density functional theory simulations are used to study the adsorption of CH4, CO2, PH3, N2O, NH3, O3, and SO2 gas molecules on a vertical hexagonal boron nitride/graphene heterostructure using the CASTEP code. Negative adsorption energy is only detected for NH3, O3, and SO2 gases. Our adsorption energy measurements show that the heterostructure is sensitive to NH3, O3, and SO2 gas molecules but insensitive to other gas molecules, as shown by the positive results. Further electrical and optical properties are only performed on gas‐adsorbed structures. It is found that the pure heterostructure acts like a semiconductor and has a band gap of 1.742 eV, which changes when gas is absorbed. Each of the structures has high absorption coefficients in the UV region, making them promising candidates for optoelectronic devices. The determination of the adsorbed gas type can be achieved by measuring the peak intensity and peak position of reflection or absorption. Heterostructures exhibit superior sensing capabilities for NH3 compared to other gases because of their enhanced adsorption energy, distinctive electrical band gap, and notable optical characteristics.

Experiment and kinetics study on OH∗ chemiluminescence up to 3150 K in hydrogen combustion behind reflected shock waves

Chemiluminescence of OH∗ is commonly employed as an optical indicator for the combustion process. It is widely recognized that the generation of OH∗ in hydrogen flames is primarily governed by the reaction H + O + M=>OH∗+M. In this study, the time histories of OH∗ chemiluminescence from the A→X band around 308 nm were recorded behind reflected shock waves for stoichiometric and lean H2/O2 mixtures highly diluted in argon over the temperature range of 1130–3150 K and at the pressure of approximately 0.9 atm. Based on the time histories of OH∗ chemiluminescence, the best-fit reaction rate coefficient for the reaction H + O + M=>OH∗+M was determined as k = 3.17 × 1027exp(-121968 cal mol−1/RT) + 2.25 × 1017exp(-4246 cal mol−1/RT) cm6 mol−2 s−1 over the temperature range studied. Furthermore, by using the current rate coefficient in mechanism predictions, the predicted time histories and relative peak intensities of OH∗ chemiluminescence are in good agreement with experimental results reported in literature.

Fabrication, surface characterization and optical behavior of flexible PVA/Nd2O3 polymer nanocomposites materials for optoelectronics applications

The nanocomposite PVA/Nd2O3 with novel properties, that composed of Neodymium (III) oxide (Nd2O3) and polyvinyl alcohol (PVA), was synthesized by the casting preparation method for applied as flexible films for optoelectronic. The techniques of the FTIR, XRD, SEM and EDX showed that the PVA/Nd2O3 were successfully synthesized. The successful inclusion of Nd2O3 into PVA is indicated by a reduction in PVA/Nd2O3 peak intensities as observed by the FTIR and XRD. Additionally, the UV/Vis technique was used to record the optical behavior at wavelengths between 200 and 1100 nm. The measurements of carbon clusters, band gap, absorption edge, and band tail were determined. The band gap decreases from 5.01 eV to 4.60 eV and the band tail changes from 1.8 eV to 2.85 eV when the Nd2O3 is raised from 5 % to 20 %. In addition, the absorption edge reduced from 5.06 eV for PVA to 4.92, 4.81, 4.72, and 4.49 eV, accordingly, when 5 %, 10 %, 15 %, and 20 % of Nd2O3 are introduced in the composite. The result showed the composites made with PVA and Nd2O3 have excellent optical characteristics, especially in the UV–visible spectrum, where they are highly reflective and absorbent. The study emphasizes the fabricated composites enhanced optical transparency and absorption properties, which make it a good materials for uses in photonic devices, sensors, and optical instruments.

Effects of off-axis angles of 4H-SiC substrates on properties of β-Ga2O3 films grown by low-pressure chemical vapor deposition

In this work, β-Ga2O3 films with (−201) preferred orientation were heteroepitaxially grown on SiC substrates with off-axis angles of 0°, 4° and 8° by low-pressure chemical vapor deposition (LPCVD). It is found that the crystal quality, surface morphology, electrical properties of the β-Ga2O3 films of the film are significantly sensitive to the off-axis angle of SiC substrates. The crystal quality and surface morphology of the film were significantly improved when the 4° off-axis substrate was used, of which the FWHM (Full width at half maximum) was as low as 0.169° and the Ra (Roughness Average) of the smooth surface was 1.98 nm. Due to the improvement of crystal quality, the Hall mobility of the films deposited on 4° off-axis substrates was increased to 50.88 cm2/V·s. The photoluminescence peak intensity of the film increases first and then decreases with the increase of the off-axis angle of the substrate. However, the use of the off-axis substrate has no obvious effect on the oxygen vacancy ratio of the films. The results of this study demonstrate the significance for the preparation of high quality heteroepitaxial β-Ga2O3 films on SiC substrate for the promising applications in power electronic and optoelectronic devices.

Understanding of the effect of concentration of green polysaccharide-based TiO2 for photoelectrochemical, photocatalytic, and antibacterial properties

Composites formed by TiO2/babassu mesocarp were synthesized by the sol-gel method with a percentage variation of 3 % and 5 % (w/v) called 3BBT and 5BBT, respectively. The materials were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV–Vis Diffuse Reflectance Spectroscopy, and surface area was calculated by the Brunauer–Emmett–Teller method (BET). Electrochemical studies were carried out, and photocurrent data was obtained as a function of the variation in gallic acid concentration and applied potential. The photocatalytic efficiency of the material was investigated by the degradation of the Methylene Blue (MB) dye under light. The antimicrobial activity of the materials was tested on Gram-positive and Gram-negative strains. XRD showed that the composites obtained are in the anatase crystallographic phase, and the increase in the percentage of babassu mesocarp influenced the reduction of peak intensity and crystallite size. The microscopy showed a more porous aspect of the 3BBT material and a denser aspect of the 5BBT material. It was confirmed by textural characterizations, which showed reduced pore volume and specific surface area of 5BBT compared to 3BBT. Increasing the percentage of polysaccharides caused a reduction in the band gap energy of TiO2 (Eg = 2.90 eV and Eg = 2.47 eV for 3BBT and 5BBT, respectively). The electrochemical study showed that the composites could detect gallic acid, providing increased sensitivity according to the increased applied photocurrent. They also showed good precision for the photoelectrochemical measurements, as verified in the repeatability test (2.66 % and 3.68 % RPD for 3BBT and 5BBT, respectively). The 3BBT showed greater photocatalytic capacity, discoloring 63.4 % of the MB dye in 120 min under light and electrons are the main species involved in photocatalytic activity demonstrated by 3BBT. Antibacterial tests indicated that the 5BBT material exhibits a greater capacity to inhibit E. coli and S. aureus bacteria.

Effect of the deposition temperature on ZnCd(SSe)2 for enhance the efficiency of solar cell application

The photoelectrochemical efficiency of ZnCd(SSe)2 thin films shows a notable enhancement, increasing from 0.08 % to 0.28 %, when deposited at different temperatures (room temperature, 40 °C, 50 °C, and 60 °C). This study aims to develop ZnCd(SSe)2 thin films using a cost-effective single-step process called the Arrested Precipitation Technique (APT). This study demonstrates that varying the deposition temperatures significantly impacts the optical, structural, and morphological properties of the resulting thin films. Optical analysis shows a reduction in the optical energy band gap from 1.92 to 1.63 eV as the bath temperature increases. X-ray diffraction confirms the formation of nanocrystalline thin film samples with improved crystallinity, as indicated by the increased intensity of the (100) diffraction peak. Scanning electron microscopy reveals changes in surface morphology corresponding to different deposition temperatures. The thin films exhibit polycrystalline characteristics, as verified by transmission electron microscopy and selected area electron diffraction pattern analysis. Energy Dispersive Spectroscopy analysis identifies the presence of Cd, Zn, S, and Se elements with near-ideal stoichiometry, suggesting a favorable composition. Importantly, the photoelectrochemical performance increases significantly from 0.08 % to 0.28 % with rising deposition temperature, marking a substantial improvement with potential for further investigation and development in the field.

Light Emission of Sn/Ge MQW pin Diodes on Si

Sn/Ge multi-quantum well diodes integrated on Si were grown pseudomorphically on Ge virtual substrates on Si using molecular beam epitaxy. Temperature-dependent electroluminescence analyses were conducted on these devices across a range of temperatures, from 290 K to 12 K. This analysis identified four distinct energy transitions across the entire temperature range. Two of the peaks were observed at high temperatures and were no longer discernible as the temperature decreased. The remaining two peaks were only measured at low temperatures. By analyzing them with a Ge reference diode, one of the peaks was identified as a defect peak. The intensity of the other peak increased as the temperature decreased, which is consistent with the behavior of a direct transition in an indirect semiconductor material.

Exploration of Volatileomics and Optical Properties of Fusarium graminearum-Contaminated Maize: An Application Basis for Low-Cost and Non-Destructive Detection.

Fusarium graminearum (F. graminearum) in maize poses a threat to grain security. Current non-destructive detection methods face limited practical applications in grain quality detection. This study aims to understand the optical properties and volatileomics of F. graminearum-contaminated maize. Specifically, the transmission and reflection spectra (wavelength range of 200-1100 nm) were used to explore the optical properties of F. graminearum-contaminated maize. Volatile organic compounds (VOCs) of F. graminearum-contaminated maize were determined by headspace solid phase micro-extraction with gas chromatography-tandem mass spectrometry. The VOCs of normal maize were mainly alcohols and ketones, while the VOCs of severely contaminated maize became organic acids and alcohols. The ultraviolet excitation spectrum of maize showed a peak redshift as fungi grew, and the intensity decreased in the 400-600 nm band. Peak redshift and intensity changes were observed in the visible/near-infrared reflectance and transmission spectra of F. graminearum-contaminated maize. Remarkably, optical imaging platforms based on optical properties were developed to ensure high-throughput detection for single-kernel maize. The developed imaging platform could achieve more than 80% classification accuracy, whereas asymmetric polarization imaging achieved more than 93% prediction accuracy. Overall, these results can provide theoretical support for the cost-effective preparation of low-cost gas sensors and high-prediction sorting equipment for maize quality detection.

Effect of various processing parameters on the properties of ZnO thin films

Zinc oxide (ZnO) thin films are essential in opto-/piezo-electronics due to their transparency, high electron mobility, wide bandgap (∼3.37 eV), and high excitonic binding energy (60 meV). Effects of processing parameters on ZnO thin films, such as the molarity, ageing, thickness, and calcination temperature, on the microstructural and optical properties deposited by sol-gel spin-coating are investigated under one roof. X-ray diffraction (XRD) confirmed the polycrystalline nature of all films, along with a dominant orientation (002) plane, indicating the formation of a c-axis oriented hexagonal wurtzite structure of ZnO regardless of the processing parameters. Peak intensities varied for all samples and exhibited the highest peak intensity annealed at 500 °C, which correlates with the increase in crystallite size from 15.93 to 16.41 nm due to a decrease in defect density via the thermal expansion. 0.4 M aged solution over 70 h showed the variation in the crystallite size and dislocation density, indicating the improvements in the thin film quality. Thickness-dependent ZnO thin films also improved the crystallinity, which was confirmed by high peak intensities. Decreasing the Urbach energy (Eu) of 0.4 M solution indicates reduced lattice imperfections/defects and high electronic quality of thin-film materials. Deposited ZnO films with an ageing time of 70 h and thickness of 109 nm exhibit the highest refractive index of 3.9 and 2.6, indicating light interaction and optimal density. The optimized conditions of sol-gel derived ZnO thin films augment the ease of development of economic devices for practical implications in opto-/piezo-electronics.

Autogenous shrinkage prediction models and microstructure of UHPC with single or binary addition of an expansive agent and steel fibers

The low water/binder ratio of ultra-high performance concrete (UHPC) often results in its high autogenous shrinkage. Our study explored the effect of the single or binary addition of a CaO-based expansive agent (CEA) and steel fibers on flowability, compressive strength, flexural strength, microstructure, and autogenous shrinkage of UHPC. X-ray diffraction (XRD), thermogravimetric (TG) analysis, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were applied to reveal the effects of CEA and steel fibers on hydration products and microstructure characteristics of UHPC. Experimental results show that the autogenous shrinkage of UHPC decreased markedly with the single or binary addition of CEA and steel fibers. Relative to the control group, autogenous shrinkage of UHPC with 2.5% dosage of single steel fibers, 6% dosage of single CEA, and binary addition of 2.5% steel fibers and 6% CEA decreased 17.8%, 10.9%, and 30.8% at 180 days, respectively. Steel fibers could enhance the mechanical performance of UHPC; nevertheless, they would decrease the flowability of UHPC. Meanwhile, the addition of CEA in the UHPC mixture not only maintained the mechanical properties and flowability but also decreased the autogenous shrinkage. Diffraction peak intensity and endothermic peak of Ca(OH)2 and the pore volume of 10–50 nm diminished with the content of CEA; however, that of C-S-H gel and ettringite increased. The prediction accuracy of nine shrinkage models (FHWA model, Lee model, Yoo model, JSCE model, B4 model, JonassonH model, Eurocode 2 model, CEB model, and DilgerW model) is analyzed with RE, Rnew2, and autogenous shrinkage of UHPC in this paper.

Analytical Spectral Semi-quantitative Dating Method of Printed Text Toner Using Raman Spectroscopy and the Fluorescence signal of Paper Sheet Cellulose

Abstract: The chemical processes that occur during the surface degradation of document paper under the influence of external factors were studied by Raman spectroscopy. The possibility of comparing the same processes occurring on clean free paper and under printed text toner letters is of interest. It is assumed that the transformation of cellulose can occur at different rates in the areas of paper exposed to direct atmospheric and light exposure and in the areas containing an intermediate layer of the toner. The most stable temporal changes occur in the region of C–C–C and C– C–O vibrations of glycosidic rings in the short-wavelength region of the Raman spectrum. Background: The main areas of research in the field of document dating, mainly focused on chromatographic methods. These methods are based on studying the dynamics of evaporation of volatile ink components. There is also a variety of chromatography techniques, including gas chromatography, ion chromatography, high performance liquid chromatography, thin layer chromatography and gas chromatography-mass spectrometry. This indicates the wide range of approaches and techniques used to determine the age of written materials. However, all these methods are used mainly during the first two years after writing the document details, which does not allow examining documents that are more than two years old. Methods: Raman spectroscopy was used as the main research method. The object of the study was sheets of white A4 paper with printed text printed on them, produced on a laser printer. The subject of the study was areas of paper free of text, as well as areas of paper under toner. The integrated fluorescence of a paper optical brightener based on stilbene was studied in the wavelength range of 400–500 nm. Also, all objects were studied using optical microscopy. Results: The comparison of peak intensity values averaged over 10 brands over the years made it possible to reveal the following regularities: – the ratio of peaks in the paper spectra from which the toner was removed is greater than in the blank paper spectra, and the difference becomes less noticeable as the age of the paper decreases. The ratio of the intensity of the 330 cm-1 peak to the intensity of the 1603 cm-1 peak: the older the document becomes, the lower the average ratios of these peaks in both the blank paper spectra and in the spectra of paper from which the toner has been removed. –the intensity of the peak in the region of 280 cm-1 and 1 086 cm-1 of the Raman shift increases with decreasing the age of the toner-free paper.– a gradual increase in the intensity of the 380 cm-1 peak is observed when comparing the paper samples from which the toner was removed for 2016, 2018, 2020, and 2022. Regularity was also found in the change in the ratio of the average statistical values of the peak at 280 cm-1 in the spectra of the paper under the toner to a similar peak in the spectra of the paper free from text: the value of this ratio decreases with decreasing the paper age. At the same time, the paper fluorescence signal is an informative parameter that makes it possible to establish some facts from the document’s history. With artificial document aging, a significant broadening of the dispersion region and the appearance of its “splitting” into two or three strata are observed in the distribution of the fluorescence signal level of a paper sheet relative to the average value. The average fluorescence signal of a naturally aged sheet decreases with the age of the document. Conclusion: As a result of research, it has been established that Raman spectroscopy can be successfully used as a method for dating documents. When comparing the degree of degradation of the surface of open areas of paper and areas protected by toner of printed text, different effects of external factors on these areas were established, leading to different rates of degradation processes. The use of Raman peak intensity ratios for paper components in exposed areas compared to peaks under printed text further expands the methodology. The emphasis on spectral methods, in particular fluorescence signal distribution and Raman spectroscopy, to detect surface changes is well justified. It demonstrates a holistic approach to document analysis, taking into account both the chemical changes observed using Raman spectroscopy and the fluorescence signal distribution that may indicate signs of artificial aging through light exposure. This combination of methods appears to be reliable for assessing the age of documents and can make significant contributions to the field of forensic document examination.

Polymer concentration adjustment for homogeneous carbon nanofibers precursors

Introduction. Carbon nanofibers CNFs have emerged as an important material in many advanced applications, especially those related to high electrical conductivity. Objectives. The primary objective of this study was to prepare a homogeneous CNFs’ precursor (Polyacrylonitrile PAN nanofibers) with improved graphitization through controlling one of the solution parameters, that is, polymer concentration. Methods. Precursors of PAN nanofibers with the addition of multi-walled carbon nanotubes MWCNTs were prepared with two concentrations of 8% and 10% w/v PAN/MWCNTs to adjust the insertion and uniform distribution of MWCNTs within the PAN nanofibers. Field emission scanning electron microscopy FESEM was used to evaluate the morphology of the electro spun nanofibers and uniformity of the MWCNTs distribution within the PAN nanofibers. Fourier transform infrared spectroscopy FTIR was also conducted to notice the interaction between MWCNTs and PAN to yield precursor with better graphitization characteristics. Results. FESEM results revealed more uniformity and homogeneity in the precursor structure with increasing PAN/MWCNTs concentration from 8% to 10% w/v. FTIR results showed increased intensity of the characteristic peaks of PAN and a new peak emerged at approximately 659 cm−1(C=C) which is potentially formed by interactions with MWCNTs and might be associated with cross-linking. Conclusion. Increased PAN/MWCNTs concentration from 8% to 10% w/v improved the insertion of MWCNTs inside PAN nanofibers and FTIR indicated the interactions between the added MWCNTs and PAN in the precursor with better graphitization characteristics.

Effect of Ag doping on the structural, morphological, optical and antibacterial activity of ZnS nanoparticles

In this study Ag-doped ZnS nanostructures for antibacterial activity were prepared by means of a facile wet-chemical method. XRD study reveals a decrease in the intensity of XRD peaks and the presence of an additional peak for silver which further affirms the incorporation of silver ions in ZnS matrix. The synthesized 1% Ag-doped ZnS nanostructures have the average particle size distribution of 16.45 ± 0.13 nm based on the TEM image. The antimicrobial activity of pure ZnS and Ag-doped ZnS were evaluated against Staphylococcus aureus and Escherichia coli. The results show that the bacterial inhibition was enhanced due to the doping of Ag into ZnS matrix in contrast to ZnS. This results obtained from the antibacterial study could be capitalized to be administered as a potent antibacterial drug for biomedical application.

Alterations in Regional Brain Microcirculation in Patients with Sepsis: A Prospective Study Using Contrast-Enhanced Brain Ultrasound.

Alterations in regional brain microcirculation have not been well studied in patients with sepsis. Regional brain microcirculation can be studied using contrast-enhanced brain ultrasound (CEUS) with microbubble administration. CEUS was used to assess alterations in regional brain microcirculation on 3 consecutive days in 58 patients with sepsis and within 24h of intensive care unit admission in 10 aged-matched nonseptic postoperative patients. Time-intensity perfusion curve variables (time-to-peak and peak intensity) were measured in different regions of interest of the brain parenchyma. The mean arterial pressure, cardiac index (using transthoracic echocardiography), global cerebral blood flow (using echo-color Doppler of the carotid and vertebral arteries), mean flow velocities of the middle cerebral arteries, and brain autoregulation (using transcranial echo-color Doppler) were measured simultaneously. The presence of structural brain injury in patients with sepsis was confirmed on computed tomography imaging, and encephalopathy, including coma and delirium, was evaluated using the Glasgow Coma Scale and the Confusion Assessment Method in the Intensive Care Unit. Of the 58 patients with sepsis, 42 (72%) developed acute encephalopathy and 11 (19%) had some form of structural brain injury. Brain autoregulation was impaired in 23 (40%) of the patients with sepsis. Brain microcirculation alterations were observed in the left lentiform nucleus and left white matter of the temporoparietal region of the middle cerebral artery in the sepsis nonsurvivors but not in the survivors or postoperative patients. The alterations were characterized by prolonged time-to-peak (p < 0.01) and decreased peak intensity (p < 0.01) on the time-intensity perfusion curve. Prolonged time-to-peak but not decreased peak intensity was independently associated with worse outcome (p = 0.03) but not with the development of encephalopathy (p = 0.77). Alterations in regional brain microcirculation are present in critically ill patients with sepsis and are associated with poor outcome. Trial registration Registered retrospectively on December 19, 2019.