A method for the direct and fast determination of oil content and humidity in olives using Fourier transform Raman spectrometry is reported. The only sample preparation step required was crushing of ...the olives using a hammer mill. The crushed olives were placed in a dedicated sample cup, which was rotated excentrically to the horizontal laser beam during spectrum acquisition. This allowed us to sample an increased volume and thus compensate for sample inhomogeneities. In this way the reproducibility of Raman spectra taken from crushed olives was significantly improved. Partial least-squares (PLS) regression was used for the chemometric evaluation of the Raman spectra. Standard errors of prediction for the validation set of 0.81% for oil content (in the range 19.68–35.71%) and 1.54% for humidity (in the range 29.23–51.49%), both expressed as weight percentage referred to fresh matter, were obtained.
The potential of Fabry Pérot Quantum Cascade (QC) lasers for transmission measurements of aqueous samples was assessed. For this purpose two lasers, one lasing in the region of the bending vibration ...of water at 1650
cm
−1, and the other in the water window at 1080
cm
−1, were used in a flow injection system comprising a dedicated fibre-optic flow cell with an adjustable path length. As test analytes a nucleic base (adenine) and a nucleoside (xanthosine) were used. Compound-specific information was obtained as the nucleoside contained a carbohydrate unit in addition to the heteroaromatic ring structure. With the laser emitting at 1650
cm
−1 the heteroaromatic ring structure of both compounds gave rise to flow injection peaks, whereas, only the nucleoside, containing the CO stretching vibrations of the carbohydrate unit, produced peaks also with the laser emitting at 1080
cm
−1. The path length limitations were investigated for both lasers. For the 1650
cm
−1 laser, path lengths up to 59
μm could be used, despite the strong absorption of water. For xanthosine analysis, the limit of detection (S/N=3) at this path length was determined to be 0.07
g
l
−1. Optical path lengths of up to 150
μm could be used for the laser emitting at 1080
cm
−1.
Microstructures constructed from SU-8 polymer and produced on CaF₂ base plates have been developed for microchip-based analysis systems used to perform FTIR spectroscopic detection using mid-IR ...synchrotron radiation. The high brilliance of the synchrotron source enables measurements at spot sizes at the diffraction limit of mid-IR radiation. This corresponds to a spatial resolution of a few micrometers (5–20 μm). These small measurement spots are useful for lab-on-a-chip devices, since their sizes are comparable to those of the structures usually used in these devices. Two different types of microchips are introduced here. The first chip was designed for time-resolved FTIR investigations of chemical reactions in solution. The second chip was designed for chip-based electrophoresis with IR detection on-chip. The results obtained prove the operational functionality of these chips, and indicate the potential of these new devices for further applications in (bio)analytical chemistry.
A morphological adaptive bilateral filter based scheme has been proposed for textures segmentation of small field digital mammograms. Mathematical morphology offers flexible operations for extraction ...of micro calcifications. Unlike the traditional texture filters, adaptive bilateral filter is applied to remove the noise and improve the quality of the selection of the different texture regions. The proposed method uses an adaptive threshold selection, which can remove unwanted textures region from image. The texture regions extract the features of micro calcification and noise boundaries are smoothing again by adaptive bilateral filter. Segmentation results are displayed by inclusion of textures with input image. The proposed method is experimented on 10 micro calcification images and the quality of the method is evaluated.
Transmission spectroscopy is a proven technique to study a transiting exoplanet's atmosphere. However, stellar surface inhomogeneities, spots and faculae, alter the observed transmission spectra: the ...stellar contamination effect. The variable nature of the stellar activity also makes it difficult to stitch together multi-epoch observations and evaluate any potential variability in the exoplanet's atmosphere. This paper introduces SAGE, a tool to correct for the time-dependent impact of stellar activity on transmission spectra. It uses a pixelation approach to model the stellar surface with spots and faculae, while fully accounting for limb-darkening and rotational line-broadening. The current version is designed for low to medium-resolution spectra. We used SAGE to evaluate stellar contamination for F to M-type hosts, testing various spot sizes and locations, and quantify the impact of limb-darkening. We find that limb-darkening enhances the importance of the spot location on the stellar disk, with spots close to the disk center impacting the transmission spectra more strongly than spots near the limb. Moreover, due to the chromaticity of limb darkening, the shape of the contamination spectrum is also altered. Additionally, SAGE can be used to retrieve the properties and distribution of active regions on the stellar surface from photometric monitoring. We demonstrate this for WASP-69 using TESS data, finding that two spots at mid-latitudes and a combined coverage fraction of \(\sim\)1% are favoured. SAGE allows us to connect the photometric variability to the stellar contamination of transmission spectra, enhancing our ability to jointly interpret transmission spectra obtained at different epochs.
Dielectric-Loaded Surface Plasmon Polariton Waveguides (DLSPPWs) offer a simple and effective solution for compact on-chip transmission and guiding of light for different optoelectronic applications. ...Especially, they offer a platform for chemical analysis enabled by efficient on-chip laser-detector coupling 1 when the optical mode guided along the sample surface is propagating (>95%) in the surrounding medium e.g. air. For longwave infrared (LWIR) applications (8-12 µm) however, the material selection is challenging as most common dielectrics like PMMA, Silica or Silicon Nitride absorb in this wavelength range 2 , 3 . As undoped Ge has low optical losses up to 14 µm, we investigated its performances as dielectric material for LWIR plasmonics.
A new interface for FT-IR analysis of liquid samples on the basis of solvent elimination is presented. The approach is based on a piezoactuated flow-through microdispenser, a device built of two ...microstructured silicon wafers designed for micro-liquid handling. It could be verified during preliminary studies using a sequential injection (SI) system for automated liquid handling that the flow-through microdispenser as a possible interface for flow system–FT-IR analysis has the capability of meeting the demands of hyphenated miniaturized liquid handling systems (e.g., μ-HPLC, microhigh performance liquid chromatography), as it successfully provides highly stable, reliable and reproducible operating conditions for liquid handling in the picoliter range. Moreover, an increase in sensitivity for FT-IR measurements could be achieved, lowering the mass detection limit of sugars (such as the investigated sucrose) to 53 picograms. As is demonstrated on the example of an HPLC separation of a mixture of glucose and fructose, interfacing LC systems to FT-IR using a piezoactuated flow-through microdispenser is a feasible and promising approach.
Mid-infrared spectroscopy together with sequential injection analysis (SIA) and partial least squares (PLS) regression analysis was used to monitor acetone-butanol-ethanol (ABE) fermentations under ...different fermentation conditions. Five analytes were simultaneously predicted (acetone, acetate, butyrate, n-butanol, and glucose). In order to compare the overall model prediction ability, a relative average of the root mean square error of prediction (RMSEP) across all five analytes was employed. To form a PLS model devoid of any cross-correlations between analytes, a synthetic calibration data set was created by the SIA system. As a test of their robustness, PLS models from synthetic samples and those from real fermentation samples were compared and used to predict samples from the opposite data set and from independent 'acid-crash' fermentations. The PLS model developed from the synthetic samples proved to be far more robust and accurate and used fewer factors than PLS models from the real fermentations, which were found to contain analyte cross-correlations. The use of synthetic data enabled more accurate selection of factors and showed the importance of investigating spectral regression coefficients plots to aid and confirm appropriate factor selection. In addition, an alternative method of factor selection was proposed, using a 'similarity measure' between the regression coefficient plots of factors for certain analytes and their standard spectra. Predictions using this method of factor selection over the common 'minimum from an error vs. factor' plot proved to be more accurate and used far fewer factors.
In this work, we present a compact high-Q factor S 3 N 4 -based Photonic Crystal Nanobeam Cavity (PhCNC) that achieves calculated Q-factors above 10 6 (experimental 10 4 ) in case over a wide range ...of upper-cladding refractive index values (1 to 1.45), angle sidewalls (0°, 5° and 7°) and stick widths. In addition, a high sensitivity (~175nm/RIU) for liquids is demonstrated.
In this work, we present a compact Si 3 N 4 Micro Ring Resonator (MRR) by introducing a Photonic Crystal (PhC) design to realize Fano lineshapes at all the resonant modes. The presented device can ...achieve experimental high-Q factor (10 4 ), and asymmetry. In addition, liquid analyte solution operation is also demonstrated.
