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Pseudo-Continuous Flow FTIR System for Glucose, Fructose and Sucrose Identification in Mid-IR Range
摘要： In this paper, we present a new FTIR-based micro?uidic system for Glucose, Fructose and Sucrose detection. The proposed micro?uidic system is based on a pseudo-continuous ?ow coupled to a microscope-FTIR instrument. The detection and characterization of sugar samples were performed by recording their absorption spectrum in the wavelength range 700–1000 cm?1 of the Mid-IR region. The proposed pseudo-continuous ?ow system is designed to improve the uniformity of the sample distribution in the analyzed area versus conventional systems. The obtained results for different sugars concentrations, show a very low measurement error of 4.35% in the absorption peak intensity, which is ten times lower than the error obtained using the conventional measurements.
关键词： mid-IR absorption spectroscopy,absorption spectrum,FTIR spectroscopy,microscopy-FTIR spectrometer,sugars detection and quanti?cation,Glucose,Fructose,Sucrose,pseudo-continuous ?ow
更新于2025-09-23 15:21:21
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A Novel Recovery Method of Soft X-ray Spectrum Unfolding Based on Compressive Sensing
摘要： In the experiment of inertial con?nement fusion, soft X-ray spectrum unfolding can provide important information to optimize the design of the laser and target. As the laser beams increase, there are limited locations for installing detection channels to obtain measurements, and the soft X-ray spectrum can be dif?cult to recover. In this paper, a novel recovery method of soft X-ray spectrum unfolding based on compressive sensing is proposed, in which (1) the spectrum recovery is formulated as a problem of accurate signal recovery from very few measurements (i.e., compressive sensing), and (2) the proper basis atoms are selected adaptively over a Legendre orthogonal basis dictionary with a large size and Lasso regression in the sense of (cid:96)1 norm, which enables the spectrum to be accurately recovered with little measured data from the limited detection channels. Finally, the presented approach is validated with experimental data. The results show that it can still achieve comparable accuracy from only 8 spectrometer detection channels as it has previously done from 14 detection channels. This means that the presented approach is capable of recovering spectrum from the data of limited detection channels, and it can be used to save more space for other detectors.
关键词： spectral measurement,spectrum unfolding,sparse representation,soft X-ray spectrometer,compressive sensing,lasso regression
更新于2025-09-23 15:21:21
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Continuous in situ measurement of dissolved methane in Lake Kivu using a membrane inlet laser spectrometer
摘要： We report the ?rst high-resolution continuous pro-?le of dissolved methane in the shallow water of Lake Kivu, Rwanda. The measurements were performed using an in situ dissolved gas sensor, called Sub-Ocean, based on a patented membrane-based extraction technique coupled with a highly sensitive optical spectrometer. The sensor was originally designed for ocean settings, but both the spectrometer and the extraction system were modi?ed to extend the dynamical range up to 6 orders of magnitude with respect to the original prototype (from nmol L?1 to mmol L?1 detection) to ?t the range of concentrations at Lake Kivu. The accuracy of the instrument was estimated to ±22 % (2σ ) from the standard deviation of eight pro?les at 80 m depth, corresponding to ±0.112 mbar of CH4 in water or ±160 nmol L?1 at 25 ?C and 1 atm. The instrument was able to continuously pro?le the top 150 m of the water column within only 25 min. The maximum observed mixing ratio of CH4 in the gas phase concentration was 77 %, which at 150 m depth and under thermal conditions of the lake corresponds to 3.5 mmol L?1. Deeper down, dissolved CH4 concentrations were too large for the methane absorption spectrum to be correctly retrieved. Results are in good agreement with discrete in situ measurements conducted with the commercial HydroC? sensor. This fast-pro?ling feature is highly useful for studying the transport, production and consumption of CH4 and other dissolved gases in aquatic systems. While the sensor is well adapted for investigating most environments with a concentration of CH4 up to a few millimoles per liter, in the future the spectrometer could be replaced with a less sensitive analytical technique possibly including simultaneous detection of dissolved CO2 and total dissolved gas pressure, for exploring settings with very high concentrations of CH4 such as the bottom waters of Lake Kivu.
关键词： Lake Kivu,dissolved methane,membrane inlet laser spectrometer,Sub-Ocean sensor,HydroC? sensor
更新于2025-09-23 15:21:01
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Indirect predissociation of highly excited singlet states of N <sub/><b>2</b> </sub>
摘要： Indirect predissociation of the b(cid:2) 1(cid:1)+u (v = 20) level of N2 is studied experimentally by vacuum-ultraviolet photoabsorption employing synchrotron radiation and a Fourier-transform spectrometer, and interpreted with the aid of a quantitative model of interacting 1(cid:2)u and 1(cid:1)+u, bound and unbound states which solves the coupled Schr?dinger equation. An observed rotationally-localised peak in the b(cid:2)(20) predissociation linewidths is identi?ed by the model as arising from an interaction with a strongly predissociated and unobserved bound level of the mixed c3 1(cid:2)u and o3 1(cid:2)u Rydberg states. This leads to the dissociation of b(cid:2)(20) into the continuum of the b 1(cid:2)u valence state. The residual observed predissociation of b(cid:2) 1(cid:1)+u (v = 20) apart from the rotationally-localised peak cannot be explained by a mechanism of 1(cid:2)u and 1(cid:1)+u interaction, and must involve states of higher multiplicity.
关键词： Fourier-transform spectrometer,coupled Schr?dinger equation,vacuum-ultraviolet photoabsorption,N2,Indirect predissociation,synchrotron radiation
更新于2025-09-23 15:21:01
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Modifying twisted nematic LCD screens to create dichromatic visual stimuli with LEDs
摘要： 1. The use of computers to create and display animations/videos in the study of visually-guided behaviors has been instrumental in understanding sensory mechanisms underlying complex traits. Using computer displays scientists are able to create a wide array of colors using three differently colored lights (Red, Green, Blue: RGB). While it is possible to generate scenes with RGB displays that mimic animals’ color perceptual experience, this can be problematic because it requires knowledge of the spectral absorbance of the animals’ photoreceptor classes, which are often unknown and are difficult to obtain. Even then, stimuli are limited to the central part of the visible spectrum (e.g., ultraviolet (UV) stimuli are not possible). 2. We present a cost-effective way of modifying a twisted nematic LCD screen that utilizes colored LEDs, that allows measuring animals’ sensitivity to, and discrimination between, wavelengths of light. It has the benefit of not requiring a-priori knowledge of animals’ photoreceptor classes. An LCD screen can be modified by removing the screen’s back polarizer (behind the liquid crystal layer) and backlighting the screen with LEDs of two different colors. One of the LED colors transmits through a polarizer with a transmission axis parallel to the screen’s front polarizer, and other LED color transmits through a polarizer orthogonal to the first. 3. To test color discrimination one can create a dichromatic stimulus in which both LED colors are ‘ON’ and the current fithrough one LED color is decreased, while the other is constant, which generated a maximum intensity contrast of 1.84 log units in our setup. To test color sensitivity one can create a monochromatic stimulus in which only one LED color is ‘ON’, which generates a contrast similar to the dichromatic stimulus. This technique overcomes many of the limitations of RGB-based LCD screens in a cost-effective way, and allows more accurate testing of the role of color in visually-guided behaviors. Besides the questions in vision research this setup can answer, it can also be used as an outreach tool in classrooms where children can learn about light, color, polarization, and technology.
关键词： twisted nematic LCD screen,spectral sensitivity,polarization,visually-guided behavior,color vision,spectrometer,LED
更新于2025-09-23 15:19:57
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Portable and benchtop Raman spectrometers coupled to cluster analysis to identify quinine sulfate polymorphs in solid dosage forms and antimalarial drug quantification in solution by AuNPs-SERS with MCR-ALS
摘要： This paper proposes for the first time: (a) a qualitative analytical method based on portable and benchtop backscattering Raman spectrometers coupled to hierarchical cluster analysis (HCA) and multivariate curve resolution – alternating least-squares (MCR-ALS) to identify two polymorphs of antimalarial quinine sulfate in commercial pharmaceutical tablets in their intact forms and (b) a quantitative analytical method based on gold nanoparticles (AuNPs) as active substrates for surface-enhanced Raman scattering (SERS) in combination with MCR-ALS to quantify quinine sulfate in commercial pharmaceutical tablets in solution. The pure concentration and spectral profiles recovered by MCR-ALS proved that both formulation present different polymorphs. These results also were confirmed by two clusters observed in HCA model, according to their similarities within and among the samples that provided useful information about homogeneity of different pharmaceutical manufacturing processes. AuNPs-SERS coupled to MCR-ALS was able to quantify quinine sulfate in the calibration range from 150.00 to 200.00 ng mL-1 even with strong overlapping spectral profile of background SERS signal, proving that is a powerful ultrahigh sensitivity analytical method. This reduced linearity was validated through a large calibration range from 25.00 to 175.00 μg mL-1 used in a reference analytical method based on high performance liquid chromatography with diode array detector (HPLC-DAD) coupled to MCR-ALS for analytical validation purposes even in the presence of coeluted compound. The analytical methods herein developed are fast, because second-order chromatographic data and first-order SERS spectroscopic data where obtained in less than 6 and 2 min, respectively. Concentrations of quinine sulfate were estimated with a low root mean square error of prediction (RMSEP) values and a low relative error of prediction (REP%) in the range 1.8-6.1%.
关键词： Quinine sulfate pharmaceutical tablets,Raman spectrometer,polymorphs,HCA and MCR-ALS,AuNPs-SERS
更新于2025-09-23 15:19:57
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Measurement performance analysis for a charge-coupled-device-based near-infrared multi-spectral pyrometer
摘要： The handheld charge coupled device (CCD) spectrometer can detect emitted, reflected or transmitted light spectrum rapidly, and so it was widely used in the fields of scientific research and industrial applications. In this paper, based on a CCD array spectrometer, a multi-spectral pyrometer is also developed, and the dependence of the spectral radiation intensity and the analog to digital converter (ADC) counts is determined by means of a blackbody furnace. Meanwhile, the noise model of the multi-spectral pyrometer is established and the influences of the readout noise, photoelectron noise and dark noise on temperature measurement accuracy are evaluated quantitatively. Experimental results show that temperature measurement accuracy is mainly affected by the readout noise. In the temperature range from 800℃ to 1200℃ and the near-infrared region around the spectral band of 780nm to 1030nm, the maximum relative temperature measurement deviation caused by the readout noise is 1.79% when the exposure time is set to 9ms. And under the same setting conditions, the maximum relative temperature measurement deviation caused by the photoelectron noise and the dark noise is 1.00% and 0.24%, respectively.
关键词： temperature measurement,noise analysis,pyrometer,spectrometer
更新于2025-09-23 15:19:57
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Simple Universal Strategy for Quantification of Carboxyl Groups on Carbon Nanomaterials: Carbon Dioxide Vapor Generation Coupled to Microplasma for Optical Emission Spectrometric Detection
摘要： The physicochemical properties and applications of carbon nanomaterials are remarkably dependent on the amount of carboxyl group on their surfaces. Unfortunately, it is challenging to determine the carboxyl group on carbon nanomaterials at an ultralow density not only due to the low sensitivities of conventional techniques, but also because there are no matrix-matched certi?ed reference materials available. In this work, a novel strategy comprising coupling carbon dioxide vapor generation to a microplasma optical emission spectrometer was developed for the sensitive and accurate quanti?cation of surface carboxyl groups on carbon nanomaterials. The carboxyl group on multiwall carbon nanotubes (MWCNTs), graphene (G), or its oxide (GO) was converted to carboxylic acid using concentrated hydrochloric acid prior to quanti?cation. The generated carboxylic acid was puri?ed and then reacted with sodium bicarbonate to generate CO2, which was swept into a miniaturized point discharge optical emission spectrometer (μPD-OES) for the detection of carbon atomic emission lines. Potassium hydrogen phthalate (KHP) served as a calibration standard for quanti?cation of the carboxyl group on G/GO/MWCNTs, thus, overcoming the lack of CRMs. Owing to the high sensitivity of μPD-OES for the detection of CO2, a limit of detection of 0.1 μmol g?1 (1 nmol) was obtained for the carboxyl group based on a sample mass of 10 mg G/GO/MWCNTs, superior to that obtained using conventional methods. Moreover, the proposed method not only retains several unique advantages of good accuracy and elimination of the use of complicated, expensive, and high power-consumption instruments, but was also applicable to the quanti?cation of the carboxyl group on other nanomaterials such as carboxylated magnetic microspheres.
关键词： carbon dioxide vapor generation,microplasma optical emission spectrometer,carbon nanomaterials,quantification,carboxyl groups
更新于2025-09-23 15:19:57
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Spectrometer-Free Graphene Plasmonics Based Refractive Index Sensor
摘要： We propose a spectrometer-free refractive index sensor based on a graphene plasmonic structure. The spectrometer-free feature of the device is realized thanks to the dynamic tunability of graphene’s chemical potential, through electrostatic biasing. The proposed sensor exhibits a 1566 nm/RIU sensitivity, a 250.6 RIU?1 figure of merit in the optical mode of operation and a 713.2 meV/RIU sensitivity, a 246.8 RIU?1 figure of merit in the electrical mode of operation. This performance outlines the optimized operation of this spectrometer-free sensor that simplifies its design and can bring terahertz sensing one step closer to its practical realization, with promising applications in biosensing and/or gas sensing.
关键词： spectrometer-free sensing,graphene plasmonics,optical refractive index sensor
更新于2025-09-23 15:19:57
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Increase of the particle hit rate in a laser single-particle mass spectrometer by pulse delayed extraction technology
摘要： A single-particle mass spectrometer (SPMS) can provide a wealth of valuable information on chemical and physical parameters of individual particles in real time. One of the main performance criteria of the instrument is efficiency of particle detection (hit rate). Most SPMS instruments use constant electrical field (DC) extraction, where stationary high voltage is applied to the extraction electrodes. As the aerosol particles initially carry a certain charge, those with a high amount to charge can be deflected by this electric field and lost, thus decreasing the hit rate. We realized that the delayed extraction technique can eliminate the stochastic dispersion of the particle beam caused by their deflection in the stationary electric field. As the result, the hit rate of the instrument can be significantly improved. Also, as the effect of the deflection in the electric field is mass dependent, it can cause distortion of the measured size distribution of the particles. Hence, the delayed extraction technique can bring the recorded distribution closer to the actual one. We found that the delayed extraction technique provides a mass resolution improvement as well as increases the hit rate. The gain in the hit rate depends on the type of particles. It can be 2 orders of magnitude for model particles and up to 2–4 times for ambient particles. In the present work we report experiments and results showing the effect of the delayed extraction on the beam divergence caused by particle charge, the hit rate improvement, and the effect of the delayed extraction on the measured particle size distribution.
关键词： hit rate,particle charge,aerosol particles,delayed extraction,single-particle mass spectrometer
更新于2025-09-23 15:19:57