Fourier-transform Spectroscopy Research Articles

Characterization of the Dielectric Parameters of Monophase Polycrystalline Bismuth Titanate Pyrochlore (Bi2Ti2O7) Ceramics and Glass-Ceramics

Pyrochlore compounds have a number of technological applications, such as dielectrics for high-frequency and magnetoelectric devices. In bulk materials, they exhibit stimulated cation arrangement and good long-distance order within the pyrochlore framework. Bismuth titanate ceramics containing SiO2 and Nd2O3 were synthesized in the Bi2O3-TiO2-SiO2-Nd2O3 system using the melt-quenching method. In a previous study, the phase composition of selected samples was determined by X-ray diffraction (XRD) analysis and the microstructure was studied by scanning electron microscopy (SEM). The preparation of monophase polycrystalline materials was concluded. Infrared Fourier-transformed spectroscopy (FTIR) was applied in order to identify the structure. The electrical conductivity, as well as the dielectric losses and dielectric constants of selected samples were determined, and the influence of the phase composition on the dielectric characteristics was evaluated. The combination of the pyrochlore phase with the amorphous phase represented by the structural groups Bi-O-Si and Si-O-Si exerts a grain boundary strengthening effect.

Emergence of meta-methylbenzyl alcohol in novel pathway of ethanol with methacrolein catalyzed by hydroxyapatite

Bioethanol, a renewable resource, can be converted into high value-added chemicals. Methylbenzyl alcohol in its ortho- and para-isomers has been successfully synthesized from ethanol upgrading over metal-modified hydroxyapatite (HAP). However, meta-methylbenzyl alcohol (3-MB-OH), a particularly valuable fine chemical, has yet to be produced from ethanol. Herein, we present a novel reaction pathway for the selective synthesis of 3-MB-OH over HAP by co-feeding ethanol with methacrolein. Notably, the selectivity of 3-MB-OH reached up to 36.2 % in our tests. Experiments using intermediates as reactants proved that the introduction of methacrolein definitively led to the production of 3-MB-OH, which was also confirmed by in-situ diffuse reflectance infrared Fourier-transform spectroscopy. Moreover, we inferred the co-conversion reaction pathway of ethanol and methacrolein. Density functional theory calculations indicated that ethanol preferentially underwent Meerwein-Ponndorf-Verley hydrogen transfer with methacrolein, resulting in acetaldehyde formation and subsequently promoting the synthesis of aromatic compounds.

Effect of Light Irradiance and Curing Duration on Degree of Conversion of Dual-Cure Resin Core in Various Cavities with Different Depths and Diameters.

(1) Background: To compare the degree of conversion of resin cores in various types of cavities and determine an effective irradiation method for achieving a higher degree of conversion. (2) Methods: Four different-sized cavities (narrow-shallow, narrow-deep, wide-shallow, and wide-deep) were simulated using a Teflon mold. The light irradiance reaching the bottom of each mold was measured by positioning a radiometer. The degree of conversion of the dual-cure resin core after irradiation (400 mW/cm2 for 20 s, 400 mW/cm2 for 40 s, and 800 mW/cm2 for 20 s) was measured using Fourier-transform near-infrared spectroscopy. (3) Results: The highest light irradiance was found at the bottom of wide-shallow cavities, followed by wide-deep, narrow-shallow, and narrow-deep ones (p < 0.001). In narrow cavities, irradiation at 800 mW/cm2 for 20 s led to a significantly higher degree of conversion (p < 0.001). In wide cavities, irradiation at 400 mW/cm2 for 40 s and 800 mW/cm2 for 20 s both led to a significantly higher degree of conversion (p < 0.001). (4) Conclusions: Less curing light reaches the bottom of cavities with a smaller diameter and greater depth. Providing a higher irradiance of light can induce a higher degree of conversion of resin composites in narrower cavities.

Controlling charge migration and CO2 conversion through surface decoration of 2D-hydrotalcite on bismuth oxybromide for enhanced artificial photosynthesis

Photocatalytic reduction of CO2 in pure H2O media to produce chemicals presents an appealing avenue for simultaneously alleviating energy and environmental crises. However, the rapid recombination of photogenerated charge carriers presents a significant challenge in this promising field. Heterojunction engineering has emerged as an effective approach to address this dilemma. Here, by decorating 2D NiAl-layered double hydroxides (NAL) onto bismuth oxybromide (BOB), we have created a S-scheme heterojunction (N1B1 composite). This catalyst affords CO2-to-CO yields of 102.30 μmol g−1 with a selectivity of 100 %. Ultraviolet photoelectron spectroscopy (UPS) and in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) reveal that charge transfer occurs efficiently from BOB to 2D-NAL upon light irradiation. The designed N1B1 heterojunction achieves 7.3-fold and 2.1-fold increase in the internal electric field strength compared to bare 2D-NAL and BOB, respectively, which should be accountable for the improved charge migration. Additionally, pulsed chemisorption and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) show the presence of multiple carbonate intermediates with activated OCO bonds upon N1B1 composite, with *CO2− being identified as the most crucial species for CO production.

Calcium Acetate Drug Produced from Rapana venosa Invasive Gastropod Shells: Green Process Control Assisted by Raman Technology.

The highly demanded calcium acetate (Ca(CH3COO)2) for biomedicine and various industries constantly requires green and low-cost methods of synthesis. In the present work, a sustainable approach to produce Ca(CH3COO)2 is reported as a proof of concept, processing for the first time as a starting material the worldwide highly abundant Rapana venosa shells, which is a neglected biogenic waste with high economical potential due to the rich mineral and organic pigmentary content. A green synthesis involving an eco-friendly acetic acid has been optimized at room temperature, without any additional energy consumption, and the resulting saturated Ca(CH3COO)2 solution was further slowly evaporated in three stages to obtain white Ca(CH3COO)2 crystalline powder, without impurity traces. Raman spectroscopy provided efficient structural information for every step of the process control, during demineralization as well as end product validation. Yields as high as 87.5% of highly pure Ca(CH3COO)2 mass have been achieved from raw R. venosa shells, proving the uniqueness and economic viability of the method. X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDX), and Fourier-Transform IR spectroscopy (FTIR) analyses validated the final product identity, hydration status, crystalline morphology, and composition. The purity of the resulting product suggests a high valorization potential of the abundant R. venosa shell in the context of the blue bioeconomy and offers a cleaner and efficient method of Ca(CH3COO)2 production with important applications in relevant industries.

Evaluation of Sentinel-5P TROPOMI Methane Observations at Northern High Latitudes

The Arctic and boreal regions are experiencing a rapid increase in temperature, resulting in a changing cryosphere, increasing human activity, and potentially increasing high-latitude methane emissions. Satellite observations from Sentinel-5P TROPOMI provide an unprecedented coverage of a column-averaged dry-air mole fraction of methane (XCH4) in the Arctic, compared to previous missions or in situ measurements. The purpose of this study is to support and enhance the data used for high-latitude research through presenting a systematic evaluation of TROPOMI methane products derived from two different processing algorithms: the operational product (OPER) and the scientific product (WFMD), including the comparison of recent version changes of the products (OPER, OPER rpro, WFMD v1.2, and WFMD v1.8). One finding is that OPER rpro yields lower XCH4 than WFMD v1.8, the difference increasing towards the highest latitudes. TROPOMI product differences were evaluated with respect to ground-based high-latitude references, including four Fourier Transform Spectrometer in the Total Carbon Column Observing Network (TCCON) and five EM27/SUN instruments in the Collaborative Carbon Column Observing Network (COCCON). The mean TROPOMI–TCCON GGG2020 daily median XCH4 difference was site-dependent and varied for OPER rpro from −0.47 ppb to 22.4 ppb, and for WFMD v1.8 from 1.2 ppb to 19.4 ppb with standard deviations between 13.0 and 20.4 ppb and 12.5–15.0 ppb, respectively. The TROPOMI–COCCON daily median XCH4 difference varied from −26.5 ppb to 5.6 ppb for OPER rpro, with a standard deviation of 14.0–28.7 ppb, and from −5.0 ppb to 17.2 ppb for WFMD v1.8, with a standard deviation of 11.5–13.0 ppb. Although the accuracy and precision of both TROPOMI products are, on average, good compared to the TCCON and COCCON, a persistent seasonal bias in TROPOMI XCH4 (high values in spring; low values in autumn) is found for OPER rpro and is reflected in the higher standard deviation values. A systematic decrease of about 7 ppb was found between TCCON GGG2014 and GGG2020 product update highlighting the importance of also ensuring the reliability of ground-based retrievals. Comparisons to atmospheric profile measurements with AirCore carried out in Sodankylä, Northern Finland, resulted in XCH4 differences comparable to or smaller than those from ground-based remote sensing.

Fourier-transform near-infrared spectroscopy first application to age determination in European fish species: the case of the Atlantic horse mackerel from the central Mediterranean Sea

Fourier-transform near-infrared spectroscopy (FT-NIRS) has recently been used to reduce the processing time for estimates of annual age in several fish species. The present study represents the first application of this technique to marine organisms from the European waters. Atlantic horse mackerel (Trachurus trachurus) from the central Mediterranean Sea was selected for its ecological role, its socioeconomic value, and because its age is regularly estimated by otolith reading under a stereomicroscope for stock assessment purposes. Absorption spectra of the whole otoliths were acquired by FT-NIRS across a multiyear dataset, obtained during acoustic surveys carried out in different regions of the central Mediterranean Sea. The acquired spectra were processed to optimize calibration models to predict age. The best linear models obtained by the optimizing procedure predicted age successfully with a coefficient of determination of 0.95–0.96, mean squared error of 0.5 years, and bias &amp;lt;0.03 years. Although regional calibration models were also obtained separately, the models with all regions combined appeared much more robust and encompassing the whole age range, suggesting its usefulness for the entire spatial distribution range considered in the preset study. The use of FT-NIRS allowed to successfully predict age for horse mackerel between the ages 1 and 14, with similar or better precision (and bias) of the traditional methods, also increasing the standardization by repeatability of age assignments. The preliminary results obtained by this study encourage further effort to fine-tune the calibration model for new species, in order to apply a precise, rapid, cost-effective method for stock assessment purposes of Mediterranean fish resources.

High-precision detection of dibutyl hydroxytoluene in edible oil via convolutional autoencoder compressed Fourier-transform near-infrared spectroscopy

The quality of edible oils is closely related to their chemical compositions. Antioxidants have widespread application in edible oil production. In this study, a pioneering detection approach involving the use of a one-dimensional convolutional autoencoder (1D-CAE) was introduced to compress spectral data for assessing antioxidant levels in edible oils. Fourier-transform near-infrared (FT-NIR) characterisation of edible oil samples with varying antioxidant concentrations was also conducted. An 1D-CAE model was developed to compress different pre-processed spectra into a condensed representation. These compressed features were then integrated with a support vector machine and partial least squares regression models to establish correlations for each target. The study examined the influence of pre-processing steps and feature engineering methods on near-infrared spectral analysis through independent or combined model analysis. The findings revealed that features derived from the 1D-CAE model demonstrated remarkable repeatability and can be utilised to construct robust detection models. The experimental results showed that the optimal detection model derived based on the 1D-CAE compression features has an average R2, RPD and RMSE of 0.9953, 15.1664 and 1.2035, respectively, on the prediction set. FT-NIR spectroscopy can be used to accurately detect butylated hydroxytoluene in edible oils. Therefore, autoencoders are an effective tool in spectroscopic analysis, offering promising avenues for future research and application.

Boosted photo-Fenton-like process for selective degradation of emerging contaminants by dehydrated Fe-based metal–organic framework with thermodynamically-favorable center metal electron density and confinement effect

The Heterogeneous Fenton reaction has long stood out as a highly effective technology for water purification. However, it is nowadays facing challenges such as low selectivity, sluggish Fe(III) reduction, and limited H2O2 conversion efficiency. Herein, dehydrated MIL-100(Fe)-250 was synthesized through thermal treatment, demonstrating superior efficiency in removing emerging contaminants, with a three-fold efficiency higher than undehydrated sample. The dehydrated MIL-100(Fe)-250 exhibited selective acceleration in the removal of quinolones and phenolic organics, rendering the system resistant to interference from coexisting matter. Through in-situ diffuse reflectance infrared Fourier-transform spectroscopy and density functional theory calculation, it was manifested that dehydration process regulates the steric hindrance and local electron density of Fe ions. This adjustment enhances charge transfer, thereby facilitating Fe(III) reduction and promoting the H2O2 activation and conversion efficiency. Moreover, the quasi-steady-state concentrations of hydroxyl radical in MIL-100(Fe)-250 were found to be 2.2 times higher than that those in undehydrated sample. Impressively, the dehydrated MIL-100(Fe)-250 displayed adaptability across a broad pH range of 5.0–9.0. The present study underscores the significant potential of porous MIL-100(Fe)-250 with spatial confinement, which imparts a clear size exclusion effect. As a result, this catalyst emerges as a promising candidate for eliminating contaminants in real water matrices, offering a viable strategy for water pollution control.

A Large-Scan-Range Electrothermal Micromirror Integrated with Thermal Convection-Based Position Sensors.

This paper presents the design, simulation, fabrication, and characterization of a novel large-scan-range electrothermal micromirror integrated with a pair of position sensors. Note that the micromirror and the sensors can be manufactured within a single MEMS process flow. Thanks to the precise control of the fabrication of the grid-based large-size Al/SiO2 bimorph actuators, the maximum piston displacement and optical scan angle of the micromirror reach 370 μm and 36° at only 6 Vdc, respectively. Furthermore, the working principle of the sensors is deeply investigated, where the motion of the micromirror is reflected by monitoring the temperature variation-induced resistance change of the thermistors on the substrate during the synchronous movement of the mirror plate and the heaters. The results show that the full-range motion of the micromirror can be recognized by the sensors with sensitivities of 0.3 mV/μm in the piston displacement sensing and 2.1 mV/° in the tip-tilt sensing, respectively. The demonstrated large-scan-range micromirror that can be monitored by position sensors has a promising prospect for the MEMS Fourier transform spectrometers (FTS) systems.

Fast and low energy-consumption integrated Fourier-transform spectrometer based on thin-film lithium niobate

Abstract Integrated miniature spectrometers have impacts in industry, agriculture, and aerospace applications due to their unique advantages in portability and energy consumption. Although existing on-chip spectrometers have achieved breakthroughs in key performance metrics, such as, a high resolution and a large bandwidth, their scanning speed and energy consumption still hinder practical applications of such devices. Here, a stationary Fourier transform spectrometer is introduced based on a Mach–Zehnder interferometer structure on thin-film lithium niobate. Long and low-loss spiral waveguides with electro-optic tuning are adopted as the optical path scanning elements with a half-wave voltage of 0.14 V. A high resolution of 2.1 nm and a spectral recovery with a bandwidth of 100 nm is demonstrated under a high-speed and high-voltage scanning in the range of −100 V to +100 V at up to 100 KHz. A low energy consumption in the μJ scale per scan is also achieved.

Temperature retrieval of near space with the combined use of O2(a1Δg) and O2(b1∑+ g) dayglow emissions under self-absorption effect correction

Atmospheric temperature information in the near space is of great academic significance and engineering value to support the development and utilization of the near space. Based on the theory of O2 molecular dayglow spectroscopy and the mechanism of atmospheric radiative transfer, a method is proposed for the joint retrieval of temperature profiles in the near space using O2(a1Δg) and O2(b1∑+g) bands dayglow spectroscopy signal with the self-absorption effect. First, the temperature dependence of O2(a1Δg) and O2(b1∑+g) bands dayglow is investigated, and the influence of the self-absorption effect on the radiative transfer characteristics is analyzed in the limb-view mode. Then, with the use of the onion peeling algorithm, the dayglow emission spectra signals of the O2(a1Δg) and O2(b1∑+g) bands measured by the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) in the limb-viewing mode were processed, and combined with optimization algorithms, the temperature profiles from 35 km to 120 km is successfully retrieved. Finally, the accuracy and reliability of the self-absorption effect correction as well as the joint temperature retrieval were verified by comparing with temperature product data from remote sensing satellites such as Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), Atmospheric Chemistry Experiment Fourier-Transform Spectrometer (ACE-FTS), and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The error analysis shows that the temperature retrieval error after correction for the self-absorption effect is about 3 K minimum and 20 K maximum.

High-performance and wavelength-transplantable on-chip Fourier transform spectrometer using MEMS in-plane reconfiguration

On-chip spectrometers with high compactness and portability enable new applications in scientific research and industrial development. Fourier transform (FT) spectrometers have the potential to realize a high signal-to-noise ratio. Here we propose and demonstrate a generalized design for high-performance on-chip FT spectrometers. The spectrometer is based on the dynamic in-plane reconfiguration of a waveguide coupler enabled by an integrated comb-drive actuator array. The electrostatic actuation intrinsically features ultra-low power consumption. The coupling gap is crucial to the spectral resolution. The in-plane reconfiguration surmounts the lithography accuracy limitation of the coupling gap, boosting the resolution to 0.2 nm for dual spectral spikes over a large bandwidth of 100 nm (1.5–1.6 μm) within a compact footprint of 75 μm×1000 μm. Meanwhile, the in-plane tuning range can be large enough for arbitrary wavelengths to ensure the effectiveness of spectrum reconstruction. As a result, the proposed spectrometer can be easily transplanted to other operation bands by simply scaling the structural parameters. As a proof-of-concept, a mid-infrared spectrometer is further demonstrated with a dual-spike reconstruction resolution of 1.5 nm and a bandwidth of 300 nm (4–4.3 μm).

Strong water-resistant Co-Mn solid solution derived from bimetallic metal–organic frameworks for catalytic destruction of toluene

The construction of Co-Mn mixed metal oxides catalysts derived from bimetallic MOFs has great significance for catalytic destruction of toluene. Hence, a series of CoaMnbOx-MOFs with different physicochemical properties were successfully synthesized via pyrolysis of Co-Mn bimetallic MOFs. Attributing to the higher specific surface area, more active sites (Co3+ and Mn3+), stronger reducibility and abundant defect sites, the as-prepared Co1Mn1Ox-MOFs dispalyed an optimal catalytic performance, especially the excellent water vapor resistance. The result of the In Situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy demonstrated that toluene can be degraded at relatively low temperatures (＜100 °C). Benzyl alcohol, benzaldehyde, benzoic acid and maleic anhydride were the main intermediate products in toluene degradation process. This work reveals the value of bimetallic MOFs derived Co-Mn oxides for toluene oxidation and presents a novel avenue for designing mixed metal oxide catalysts with potential applications in VOCs catalytic oxidation.

Applying Spatial Metabolomics To Investigate Age- and Drug-Induced Neurochemical Changes.

In an era when population aging is increasing the burden of neurodegenerative conditions, deciphering the mechanisms underlying brain senescence is more important than ever. Here, we present a spatial metabolomics analysis of age-induced neurochemical alterations in the mouse brain using negative ionization mode mass spectrometry imaging. The age-dependent effects of the acetylcholinesterase inhibitor tacrine were simultaneously examined. For ultrahigh mass resolution analysis, we utilized a Fourier-transform ion cyclotron resonance spectrometer. To complement this, a trapped ion mobility spectrometry time-of-flight analyzer provided high speed and lateral resolution. The chosen approach facilitated the detection and identification of a wide range of metabolites, from amino acids to sphingolipids. We reported significant, age-dependent alterations in brain lipids which were most evident for sulfatides and lysophosphatidic acids. Sulfatide species, which are mainly localized to white matter, either increased or decreased with age, depending on the carbon chain length and hydroxylation stage. Lysophosphatidic acids were found to decrease with age in the detailed cortical and hippocampal subregions. An age-dependent increase in the glutamine/glutamate ratio, an indicator of glia-neuron interconnection and neurotoxicity, was detected after tacrine administration. The presented metabolic mapping approach was able to provide visualizations of the lipid signaling and neurotransmission alterations induced by early aging and can thus be beneficial to further elucidating age-related neurochemical pathways.

New Iron(III)-Containing Composite of Salinomycinic Acid with Antitumor Activity—Synthesis and Characterization

In this study we demonstrated for the first time synthetic procedures for composites of salinomycin (SalH) and two-line ferrihydrite. The products were characterized by various methods such as elemental analysis, attenuated total reflectance–Fourier-transform spectroscopy (ATR-FTIR), electron paramagnetic resonance spectroscopy (EPR), powder X-ray diffraction analysis (XRD), electrospray-ionization mass spectrometry (ESI-MS), thermogravimetric analysis with differential thermal analysis (DTA) and mass spectrometry (TG-DTA/MS). The EPR spectra of the isolated compounds consisted of signals associated with both isolated Fe3+ ions and magnetically coupled Fe3+ ions. Powder XRD analyses of the isolated products showed two intense and broad peaks at 9° and 15° 2Θ, corresponding to salinomycinic acid. Broad peaks with very low intensity around 35°, assigned to two-line ferrihydrite, were also registered. Based on the experimental results, we concluded that salinomycin sodium reacted with Fe(III) chloride to form composites consisting of two-line ferrihydrite and salinomycinic acid. One of the composites exerted pronounced antitumor activity in the sub-micromolar concentration range against human cervical cancer (HeLa), non-small-cell lung cancer (A549), colon cancer (SW480), and ovarian teratocarcinoma (CH1/PA1) cells.

Fast spectroscopic imaging using extreme ultraviolet interferometry.

Extreme ultraviolet pulses as generated by high harmonic generation (HHG) are a powerful tool for both time-resolved spectroscopy and coherent diffractive imaging. However, the integration of spectroscopy and microscopy to harness the unique broadband spectra provided by HHG is hardly explored due to the challenge to decouple spectroscopic and microscopic information. Here, we present an interferometric approach to this problem that combines Fourier transform spectroscopy (FTS) with Fourier transform holography (FTH). This is made possible by the generation of phase-locked pulses using a pair of HHG sources. Crucially, in our geometry the number of interferometric measurements required is at most equal to the number of high-harmonics in the illumination, and can be further reduced by incorporating prior knowledge about the structure of the FTH sample. Compared to conventional FTS, this approach achieves over an order of magnitude increase in acquisition speed for full spectro-microscopic data, and furthermore allows high-resolution computational imaging.

Compact Spatial Heterodyne Spectrographs for Future Space-Based Observations: Instrument Modeling and Applications.

High-resolution spectroscopy employing spatial heterodyne spectrographs (SHS) holds significant promise for forthcoming space missions, building upon its established track record in science applications. Notably, it offers exceptional performance and cost- effectiveness in the ultraviolet-visual (UV-Vis) region compared to contemporary instruments. SHS instruments provide high-resolution capabilities and substantially larger etendues than similar resolving power instruments. This study introduces a comprehensive Python-based SHS model integrated with a user-friendly web scraping interface for target star selection, parameter generation, and 2D interferogram creation. Our SHS model demonstrates double the resolving power of a grating spectrometer and a throughput comparable to a Fourier transform spectrometer (FTS) but without moving parts, enhancing robustness for deployment in space. The interferogram processing algorithm includes flat-fielding, bias removal, apodization, and an inverse Fourier transform (IFT) for accurate spectrum retrieval. Despite bandwidth limitations due to resolving power constraints, SHS models excel in applications requiring high spectral resolution over narrow wavelength ranges, such as studying isotopic emission lines. The model provides optimization results and trade-offs for system parameters, ensuring precise spectral recovery with realistic signal-to-noise ratio (SNR) values. SHS is versatile and effective for various scientific applications, including investigating atomic and molecular emissions from comets, planetary atmospheres, the Earth's atmosphere, the Sun, and the interstellar medium (ISM). This research significantly contributes to expediting the development and deployment of SHS instruments, demonstrating their potential across numerous scientific domains.

Properties of supernova remnants in SIGNALS galaxies – I. NGC 6822 and M33

Abstract We present a spatially resolved study of the kinematical properties of known supernova remnants (SNRs) in the nearest galaxies of the SIGNALS survey, namely NGC 6822 (one object) and M33 (163 objects), based on data obtained with the SITELLE Imaging Fourier Transform Spectrometer (iFTS) at the Canada-France-Hawaii Telescope. The purpose of this paper is to provide a better scheme of identification for extragalactic SNRs and, in particular, to distinguish between H ii regions and SNRs. For that we have used diagrams which involve both the [S ii]/Hα ratio and the velocity dispersion (σ). We also introduce a new parameter, $\xi = {[\rm S\, \small {II}] \over H\alpha } \times \sigma$, which enhances still the contrast between SNRs and the rest of the ionised gas. More than 90% of the SNRs in our entire sample show an integrated [S ii]/Hα ratio larger than the canonical value (0.4). 86% of the SNRs present in our field show a significant velocity dispersion. The spectral resolution of our observations allows us to observe the complex velocity structure of some SNRs.

A new and fast method for diabetes and dyslipidemia diagnosis using FTIR-MIR, spectroscopy and multivariate data analysis: A proof of concept

Diabetes and dyslipidemia are well-established risk factors for cardiovascular disease, which is the primary cause of death both in Brazil and globally. Fourier-transform mid-infrared spectroscopy (FTIR-MIR) generates spectral fingerprints of biomolecules, allowing for correlation with metabolic changes, while remaining a rapid, non-invasive, and non-destructive method. The study provided a proof of concept for the effectiveness of FTIR-MIR in screening diabetes, pre-diabetes, hypercholesterolemia, hypertriglyceridemia, and mixed dyslipidemia in blood serum. After acquiring mid-infrared spectra of 60 human serum samples, both unsupervised and supervised analysis models were developed. Principal component analysis (PCA) was used for pattern recognition and to determine how closely related the samples were based on their spectral profiles. The results obtained by the supervised models showed a clear discriminative ability to distinguish both diabetic and dyslipidemic samples from healthy subjects by multivariate analysis performed on FTIR-MIR spectra. High accuracy rates of more than 90 % were achieved for diabetes and dyslipidemia diagnosis with PLS-DA. Dyslipidemia type discrimination could be attributed mainly to the amide I region [1720-1600 cm−1, (ν(CO)] and altered lipid concentration in the 3000-2800 cm−1 region, whereas the discrimination of diabetes and prediabetes was primarily due to the altered conformational protein in the Amides I [1720-1600 cm−1, ν(CO)] and Amide II [1570-1480 cm−1, δ(NH) + ν(CH)] range.