Search Results (55)

The present study explores a multi-analytical non-invasive approach based on the application of terahertz continuous wave (THz-CW) spectroscopy for the non-invasive characterization of historically produced synthetic copper silicate pigments. For the first time, Han Blue, Han Purple and Egyptian Blue were examined within the THz spectral region using a compact and portable THz-CW spectrometer. The three pigments exhibit distinct absorption features, which facilitate the differentiation of molecular structures within the same chemical and mineralogical category. Moreover, the same compound was analyzed using Energy Dispersive X-Ray Fluorescence (ED-XRF) to determine its elemental composition, alongside Fiber Optics Reflectance Spectroscopy (FORS) in the range 350–2500 nm, providing crucial insights into its optical properties and molecular structure. To the best of the authors’ knowledge, the present study presents the first spectra for these copper silicates at these wavelengths, thereby expanding the shortwave infrared spectral database of Cultural Heritage materials. This synergistic approach enables a comprehensive characterization, offering a deeper understanding of the compounds’ chemical nature and paving the way for potential applications in the Cultural Heritage domain. Furthermore, the findings underscore the potential of THz-CW spectroscopy as an innovative and effective tool for Cultural Heritage research, providing a non-destructive method to investigate artistic materials. Full article

A flash smelting furnace operation is based on the exothermic reduction of copper concentrates in the combustion shaft, and these reactions occur at high temperatures (1250–1350 °C), where flame control is fundamental to optimizing copper reduction. Furthermore, inherent physicochemical reactions of the reduction process have been shown to emit spectral lines in the visible-near infrared spectrum (250–900 nm). Thus, an optoelectronic sensor prototype is proposed and developed for flame measurements of an industrial copper concentrate flash smelting furnace. The sensor system is composed of a high-temperature optical fiber probe, which functions as a waveguide to capture the emitted flame radiation and a visible-near infrared spectrometer. From the measured radiation, flame temperature and flame dynamics are analyzed. Flame temperature is estimated using the two-wavelength temperature estimation method, and flame dynamics are defined as variations in the total emissive power, which are studied in the time and frequency domain via the Fourier Transform method. These combustion dynamics are then used to create a flame instability index, which is used to characterize the flame combustion quality. The combination of this index and sensor platform provides a powerful tool to aid in proper flame control. Full article

Mid-infrared spectral analysis has long been recognized as the most accurate noninvasive blood glucose measurement method, yet no practical compact mid-infrared blood glucose sensor has ever passed the accuracy benchmark set by the USA Food and Drug Administration (FDA): to substitute for the finger-pricking glucometers in the market, a new sensor must first show that 95% of their glucose measurements have errors below 15% of these glucometers. Although recent innovative exploitations of the well-established Fourier-transform infrared (FTIR) spectroscopy have reached such FDA accuracy benchmarks, an FTIR spectrometer is too bulky. The advancements of quantum cascade lasers (QCLs) can lead to FTIR spectrometers of reduced size, but compact QCL-based noninvasive blood glucose sensors are not yet available. This work reports on two compact sensor system designs, both reaching the FDA accuracy benchmark. Each design commonly comprises a mid-infrared QCL for emission, a multiple attenuation total reflection prism (MATR) for data acquisition, and a computer-controlled infrared detector for data analysis. The first design translates the comb-like signals into conventional spectra, and then data-mines the resultant spectra to yield blood glucose concentrations. When a pressure actuator is employed to press the patient’s hypothenar against the MATR, the sensor accuracy is considered to reach the FDA accuracy benchmark. The second design abandons the data processing step of translating combs-to-spectra and directly data-mines the “first-hand” comb signal. Beyond increasing the measurement accuracy to the FDA accuracy benchmark, even without a pressure actuator, direct comb data-mining upgrades the sensor system with speed and data integrity, which can impact the healthcare of diabetic patients. Specifically, the sensor performance is validated with 492 glucose absorption scans in the time domain, each with 20 million datapoints measured from four subjects with glucose concentrations of 3.9–7.9 mM. The sensor data-mines 164 sets of critical singularity strengths, each comprising 4 critical singularity strengths directly from the 9840 million raw signal datapoints, and the 656 critical singularity strengths are subjected to a machine-learning regression model analysis, which yields 164 glucose concentrations. These concentrations are correlated with those measured with a standard finger-pricking glucometer. An accuracy of 99.6% is confirmed from the 164 measurements with errors not more than 15% from the reference of the standard glucometer. Full article

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in hundreds of millions of infections and millions of deaths globally. Although vaccination campaigns are mitigating the pandemic, emerging viral variants continue to pose challenges. The spike (S) protein of SARS-CoV-2 plays a critical role in viral entry by binding to the angiotensin-converting enzyme 2 (ACE2) receptor, making both proteins essential targets for therapeutic and vaccine development. The glycosylation of these proteins influences their structure and function. This underscores the need for detailed site-specific glycoproteomic analysis. In this study, we characterized the N- or O-glycosylation profiles of the recombinant receptor-binding domain (RBD) of spike protein and ACE2 proteins expressed from Expi293F cells, as well as the S2 subunit of spike protein expressed in plant (N. benthamiana) cells. Using a high-resolution Orbitrap Eclipse Tribrid mass spectrometer equipped with the Ultimate 3000 RSLCnano and I-GPA (Integrated GlycoProteome Analyzer) developed in a previous study, 148 N- and 28 O-glycopeptides from RBD, 71 N-glycopeptides from the S2 subunit, and 139 N-glycopeptides from ACE2 were characterized. In addition, we report post-translational modifications (PTMs) of glycan, including mannose-6-phosphate (M6P) and GlcNAc-1-phosphate-6-O-mannose in N-glycan of RBD and ACE2, and O-acetylation in O-glycan of RBD, identified for the first time in these recombinant proteins. The relative abundance distribution according to glycosites and glycan types were analyzed by quantified site-specific N- and O (only from RBD)-glycopeptides from RBD, S2, and ACE2 using I-GPA. Asn331 for RBD, Asn1098 for S2, and Asn103 for ACE2 were majorly N-glycosylated, and dominant glycan-type was complex from RBD and ACE2 and high-mannose from S2. These findings will provide valuable insights into the glycosylation patterns that influence protein function and immunogenicity and offer new perspectives for the development of vaccines and antibody-based therapies against COVID-19. Full article

Remote sensing is a valuable tool in precision agriculture due to its spatial and temporal coverage, non-destructive method of data collection, and cost-effectiveness. In this study, we measured the canopy reflectance of potato (Solanum tuberosum L.) crops on a plant-by-plant basis with a handheld spectrometer instrument. Our study pursues two primary objectives: (1) determining the optimal temporal aggregation for measuring canopy signals related to potato yield and (2) identifying the best spectral bands in the 350–2500 nm domain and vegetation indices. The study was conducted over two consecutive years (2020 and 2021) with 60 plants per plot, encompassing six potato varieties and three replicates annually throughout the growth season. Employing correlation analysis and dimensionality reduction, we identified 23 independent features significantly correlated with tuber yield. We used multiple linear regression analysis to model the relationship between the selected features and yield and to compare their influence in the fitted model. We used the Leave-One-Out Cross-Validation (LOOCV) method to assess the validity of the model (RMSE = 702 g and %RMSE = 29.2%). The most significant features included the Gitelson2 and Vogelmann indices. The optimal time period for measurements was determined to be from 56 to 100 days after planting. These findings may contribute to the advancement of precision farming by proposing tailored sensor applications, paving the way for improved agricultural practices and enhanced food security. Full article

As atmospheric CO₂ emissions and the trend of urbanization both increase, the ability to accurately assess the CO₂ budget from urban environments becomes more important for effective CO₂ mitigation efforts. This task can be difficult for complex areas such as the urban–coastal Mediterranean region near Marseille, France, which contains the second most populous city in France as well as a broad coastline and nearby mountainous terrain. In this study, we establish a CO₂ modeling framework for this region for the first time using WRF-Chem and demonstrate its efficacy through comparisons against cavity-ringdown spectrometer measurements recorded at three sites: one 75 km north of the city in a forested area, one in the city center, and one at the urban/coastal border. A seasonal CO₂ analysis compares Summertime 2016 and Wintertime 2017, to which Springtime 2017 is also added due to its noticeably larger vegetation uptake values compared to Summertime. We find that there is a large biogenic signal, even in and around Marseille itself, though this may be a consequence of having limited fine-scale information on vegetation parameterization in the region. We further find that simulations without the urban heat island module had total CO₂ values 0.46 ppm closer to the measured enhancement value at the coastal Endoume site during the Summertime 2016 period than with the module turned on. This may indicate that the boundary layer on the coast is less sensitive to urban influences than it is to sea-breeze interactions, which is consistent with previous studies of the region. A back-trajectory analysis with the Lagrangian Particle Dispersion Model found 99.83% of emissions above 100 mol km⁻² month⁻¹ captured in Summer 2016 by the three measurement towers, providing evidence of the receptors’ ability to constrain the domain. Finally, a case study showcases the model’s ability to capture the rapid change in CO₂ when transitioning between land-breeze and sea-breeze conditions as well as the recirculation of air from the industrial Fos region towards the Marseille metroplex. In total, the presented modeling framework should open the door to future CO₂ investigations in the region, which can inform policymakers carrying out CO₂ mitigation strategies. Full article

There is an increasing need for compact low-cost NMR apparatus that can be used on the laboratory bench and in the field. There are four main usage variants of usage: (a) time-domain apparatus, particularly for physical measurements; (b) frequency-domain apparatus, particularly for chemical analysis, (c) NMR Cryoporometry apparatus for measuring pore-size distributions; and (d) MRI apparatus for imaging. For all of these, variable temperature capability may be vital. We have developed compact low-cost apparatus targeted at these applications. We discuss a hand-held NMR Spectrometer, and three different holdable NMR magnets, with sufficiently large internal bores for the Lab-Tools compact Peltier thermo-electric cooled variable-temperature probes. Currently, the NMR Spectrometer is very suitable for (a) NMR time-domain relaxation and (c) NMR Cryoporometry. With a suitable high-homogeneity magnet, it is also appropriate for simple use (b), spectral analysis, or, with a suitable gradient set, (d) MRI. Together, the NMR Spectrometer, one of the NMR variable-temperature probes, and any of these NMR magnets make excellent NMR Cryoporometers, as demonstrated by this paper and previously published research. Equally, they make versatile general-purpose variable-temperature NMR systems for materials science. Full article

As artificially engineered subwavelength periodic structures, terahertz (THz) metasurface devices exhibit an equivalent dielectric constant and dispersion relation akin to those of natural materials with specific THz absorption peaks, describable using the Lorentz model. Traditional verification methods typically involve testing structural arrays using reflected and transmitted optical paths. However, directly detecting the dielectric constant of individual units has remained a significant challenge. In this study, we employed a THz time-domain spectrometer-based scattering-type scanning near-field optical microscope (THz-TDS s-SNOM) to investigate the near-field nanoscale spectrum and resonant mode distribution of a single-metal double-gap split-ring resonator (DSRR) and rectangular antenna. The findings reveal that they exhibit a dispersion relation similar to that of natural materials in specific polarization directions, indicating that units of THz metasurface can be analogous to those of molecular structures in materials. This microscopic analysis of the dispersion relation of artificial structures offers new insights into the working mechanisms of THz metasurfaces. Full article

Tunability of properties is one of the most important features of 2D materials, among which graphene is attracting the most attention due to wide variety of its possible applications. Here, we demonstrated that the carrier concentration in graphene can be efficiently tuned by the material of the dielectric substrate on which it resides. To this end, we fabricated samples of CVD-grown graphene transferred onto silicon wafers covered with alumina, titanium dioxide, and silicon dioxide. We measured the transmission spectra of these samples using a time-domain terahertz spectrometer and extracted the Drude frequency-dependent graphene conductivity. We found that the sheet resistance of graphene is strongly affected by the underlying dielectric material, while the carrier scattering time remains the same. The carrier concentration value was found to range from $7\times {10}^{11}/{\mathrm{c}\mathrm{m}}^2$ in the case of alumina and $4.5\times {10}^{12}/{\mathrm{c}\mathrm{m}}^2$ in the case of titanium dioxide. These estimations are consistent with what can be extracted from the position of the G-peak in the Raman spectra of graphene. Our results show a way to control the graphene doping level in applications where it does not have to be adjusted. Full article

Iron isotope compositions, along with the partial extraction of iron in its various forms, can be utilized to investigate the complex interplay of iron migration and transformation with respect to iron isotope patterns. This study investigated the iron composition of a typical loess-paleosol sequence in Northeast China and aimed to understand the influence of iron migration and transformation of the typical loess-paleosol sequence on iron isotopes and environmental and climatic changes that occurred in the region over time by analyzing the distribution and characteristics of iron compositions in sedimentary layers. Samples were collected from Chaoyang in Northeast China, and the iron isotopic composition was analyzed using the multi-receiver inductively coupled plasma mass spectrometer (MC-ICP-MS). The findings revealed depth-dependent variations in the content of different iron forms, reflecting paleoclimatic shifts primarily through pedogenic transformation processes. Notably, iron migration within the section was observed to be limited. The variations in the reddening index and magnetic susceptibility of the loess-paleosol were primarily influenced by the presence of free iron (Fed), exhibiting a range of colors from yellow to red-yellow and red. The δ⁵⁶Fe values for loess and paleosols ranged from 0.097 ± 0.035‰ to 0.167 ± 0.010‰, with an average of 0.133 ± 0.024‰ and a coefficient of variation (CV) of 15.66% at the stratum scale. These values indicated a systematic enrichment of heavy iron isotopes and a significant negative correlation with the slightly fluctuating total iron content. Specifically, our analysis highlighted distinct differences in δ⁵⁶Fe values between paleosol (0.126 ± 0.024‰) and loess (0.146 ± 0.021‰). The δ⁵⁶Fe in Fed was negative, averaging −0.101 ± 0.022‰, while the δ⁵⁶Fe in silicate-bound iron was positive, averaging 0.156 ± 0.032‰. Intense pedogenesis, driven by warm and wet climates, facilitated iron transformations and migrations, resulting in the accumulation of light iron isotopes in the paleosols. These transformations and migrations were predominantly observed in microdomains characterized by iron depletions and concentrations, as reflected in the profile morphologies. However, the limited iron transformations and migrations did not result in significant Fe redistribution within the soil section, as evidenced by the limited variations in δ⁵⁶Fe with soil depth at the stratum scale. Sampling from the stratum or pedogenic horizon could potentially create the illusion of the minimal fractionation of iron isotopes within the sequence. Therefore, a detailed examination of the iron isotope composition in the micro-domains of the loess-paleosol sequence is crucial to elucidate the fractionation processes and mechanisms of iron isotopes during the formation of these sequences. Full article

This work presents results on laser-induced surface structuring of AlN ceramic and its application in Surface-Enhanced Raman Spectroscopy (SERS). The laser processing is performed by nanosecond pulses in air and vacuum. Depending on the processing conditions, different surface morphology can be obtained. The ablation process is realized by ceramic decomposition as the formation of an aluminium layer is detected. The efficiency of the fabricated structures as active substrates in SERS is estimated by the ability of the detection of ammonium nitrate (NH₄NO₃). It is conducted for Raman spectrometer systems that operate at wavelengths of 514 and 785 nm where the most common commercial systems work. The obtained structures contribute to enhancement of the Raman signal at both wavelengths, as the efficiency is higher for excitation at 514 nm. The limit of detection (LOD) of ammonium nitrate is estimated to be below the maximum allowed value in drinking water. The analysis of the obtained results was based on the calculations of the near field enhancement at different conditions based on Finite Difference Time Domain simulation and the extinction spectra calculations based on Generalized Mie scattering theory. The structures considered in these simulations were taken from the SEM images of the real samples. The oxidation issue of the ablated surface was studied by X-ray photoelectron spectroscopy. The presented results indicated that laser structuring of AlN ceramics is a way for fabrication of Al structures with specific near-field properties that can be used for the detection of substances with high social impact. Full article

We demonstrate a sensing scheme for liquid analytes that integrates multiple optical fiber sensors in a near-infrared spectrometer. With a simple optofluidic method, a broadband radiation is encoded in a time-domain interferogram and distributed to different sensing units that interrogate the sample simultaneously; the spectral readout of each unit is extracted from its output signal by a Fourier transform routine. The proposed method allows performing a multiparametric analysis of liquid samples in a compact setup where the radiation source, measurement units, and spectral readout are all integrated in a robust telecom optical fiber. An experimental validation is provided by combining a plasmonic nanostructured fiber probe and a transmission cuvette in the setup and demonstrating the simultaneous measurement of the absorption spectrum and the refractive index of water–methanol solutions. Full article

In order to capture the large-scale interferometric signal generated by the space-borne interferometric infrared Fourier spectrometer (IRIFS) in real time, and overcome the limitations of insufficient sampling rate, transmission rate, and significant signal noise in current equipment, a multi-channel high-speed acquisition system for large-scale interferometric signals is designed. A high-performance analog-to-digital converter (ADC) oversampling scheme is designed, which can realize up to 8 synchronous acquisition channels and has a maximum sampling rate of 125 Msps/Ch to ensure the acquisition of interferometric signals. The scheme of jesd204b inter-board transmission and optical fiber terminal transmission is designed. The inter-board transmission rate is 12.5 Gbps, and the terminal transmission rate is 10 GB/s to ensure high-speed data transmission. A hardware filter is designed to realize spatial noise processing of interference signals and ensure the accuracy of acquisition results. The dynamic performance of the data acquisition (DAQ) card is analyzed using discrete Fourier transform in the frequency domain. The spurious free dynamic range (SFDR) is 84 dB, the signal-to-noise ratio (SNR) is 72.7 dB, and the cross-talk is −81.6 dB, which verifies the dynamic stability of the DAQ card. Finally, the infrared radiation in real space is measured. The average ${\Delta }_{NESR}$ of long wave reaches 48 $\mathrm{mW}\ast {\mathrm{m}}^{-2}\ast {\mathrm{sr}}^{-1}$, and the average ${\Delta }_{NESR}$ of medium wave reaches 12.3 $\mathrm{mW}\ast {\mathrm{m}}^{-2}\ast {\mathrm{sr}}^{-1}$, which verifies the reliability of the system performance. The system is of great significance for large-scale infrared interferometric signal acquisition, and has strong practical application value in multi-channel synchronization, real-time high-speed acquisition, and high-speed data transmission. Full article

In this research, benzoxazine (BA-a) and diamino polysiloxane (PSX750) blends were prepared at 0–50 wt% of BA-a. The interactions between two polymeric components were investigated via a Fourier Transform Infrared Spectrometer (FT-IR). The thermal properties of the blends were also determined with Dynamic Mechanical Analyzer (DMA) and Thermogravimetric Analyzer (TGA). The mechanical properties and shape memory behaviors of the blends were also investigated. The FTIR spectra exhibited the shift of the peak from 1672 to the range of 1634–1637 cm⁻¹, which could be identified as hydrogen bonds between two polymeric domains at the contents from 30 to 50 wt%. The DMA thermograms revealed two glass transition temperatures, which could indicate a partially miscible system. The char yield values were increased, while the decomposition temperatures were decreased with an increasing benzoxazine content. Interestingly, the blends at the contents of 10 and 20 wt% presented dual-shape memory behaviors, whereas triple- or multiple-shape memory behaviors were observed with benzoxazine contents of 30 to 50 wt%. For the high-temperature recovery state, a shape memory ratio of 97.5% with a recovery time of 65 s and a shape fixity ratio of 66.7% was recorded at the content of 50 wt%. For the low-temperature recovery state, a shape recovery ratio of 98.9% was observed at the same content. Moreover, the values of the recovery ratio for four shape-recovery cycles revealed multiple shape memory behaviors with high recovery ratios in the range of 95–98%. Full article

The airborne hyperspectral remote sensing systems (AHRSSs) acquire images with high spectral resolution, high spatial resolution, and high temporal dimension. While the AHRSS captures more detailed information from the terrain objects, the computational complexity of data processing is greatly increased. As an important application technology in the hyperspectral domain, anomaly detection (AD) processing must be real-time and high-precision in many cases, such as post-disaster rescue, military battlefield search, and natural disaster detection. In this paper, the real-time AD technology for the push-broom AHRSS is studied, the mathematical model is established, and a novel implementation framework is proposed. Firstly, the optimized kernel minimum noise fraction (OP-KMNF) transformation is employed to extract informative and discriminative features between the background and anomalies. Secondly, the Nyström method is introduced to reduce the computational complexity of OP-KMNF transformation by decomposing and extrapolating the sub-kernel matrix to estimate the eigenvector of the entire kernel matrix. Thirdly, the extracted features are transferred to hard disks for data storage. Then, taking the extracted features as input data, the background separation model-based CEM anomaly detector (BSM-CEMAD) is imported to detect anomalies. Finally, graphics processing unit (GPU) parallel computing is utilized in the Nyström-based OP-KMNF (NOP-KMNF) transformation and the BSM-CEMAD to improve the execution efficiency, and the real-time AD for the push-broom AHRSS could be realized. To test the feasibility of the implementation framework proposed in this paper, the experiment is carried out with the Airborne Multi-Modular Imaging Spectrometer (AMMIS) developed by the Shanghai Institute of Technical Physics as the data acquisition platform. The experimental results show that the proposed method outperforms many other state-of-the-art AD methods in anomalies detection and background suppression. Moreover, under the condition that the downlink data could retain most of the hyperspectral data information, the proposed method achieves real-time detection of pixel-level anomalies, with the initial delay not exceeding 1 s, the false alarm rate (FAR) less than 5%, and the true positive rate (TPR) close to 98%. Full article