The vibrational spectrum of calcite (CaCO3) is evaluated at an ab initio periodic quantum-mechanical level by using the CRYSTAL package. A localized basis set of Gaussian-type functions and the B3LYP hybrid Hamiltonian are adopted. The dynamical matrix is obtained by differentiating numerically the analytical first derivatives of the energy. The accuracy with respect to all computational parameters is documented. The calculated frequencies are compared with available IR and RAMAN data (16 and 5 peaks, respectively), the mean absolute error being less than 12 cm−1 (frequencies range from 100 to 1600 cm−1). Overall, the agreement with experiment is very satisfactory, and shows that simulation can produce at a relatively low cost the full spectra of crystalline compounds of mineralogical interest.

The vibrational spectrum of calcite (CaCO3): an ab initio quantum-mechanical calculation Note: Theoretically derived structure

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Process Heat Transfer

Background Food quality and safety are very important from health as well as fiscal point of view. Surface-enhanced Raman spectroscopy (SERS) techniques have unique advantages in the field of food detection , with characteristics of fast analysis speed, high detection sensitivity, and without interference from the water phase. Scope and approach In this review, recent and potential advances in the application of SERS in food safety and quality from the perspective of SERS substrate and SERS composite systems are addressed. SERS systems such as molecular labeling, immunochromatographic assay, microfluidics, molecularly imprinted polymers, colorimetry and imaging are discussed, and their main advantages and limitations are highlighted. The applications of SERS in food safety are reviewed critically, with focus on the detection of microorganisms, pesticides, metal ions and antibiotics. Furthermore, applications of SERS in food quality regarding food freshness and ingredients are discussed. Key findings and conclusions SERS technology has been widely used in food testing, but it still has shortcomings. In order to establish SERS as a routine tool for the monitoring of food safety and quality, future research should focus on minimizing technical costs, standardizing experimental protocols, developing new SERS substrates, and integrating SERS with other methods to overcome its shortcomings.

Evolving trends in SERS-based techniques for food quality and safety: A review

Surface-enhanced Raman scattering (SERS) and photoluminescence (PL) are important photoexcitation spectroscopy techniques; however, understanding how to analyze and modulate the relationship between SERS and PL is rather important for enhancing SERS, having a great effect on practical applications. In this work, a charge-transfer (CT) mechanism is proposed to investigate the change and relationships between SERS and PL. Analyzing the change in PL and SERS before and after the adsorption of the probe molecules on Nd-doped ZnO indicates that the unique optical characteristics of Nd3+ ions increase the SERS signal. On the other hand, the observed SERS can be used to explain the cause of PL background reduction. This study demonstrates that modulating the interaction between the probe molecules and the substrate can not only enhance Raman scattering but also reduce the SERS background. Our work also provides a guideline for the investigation of CT as well as a new method for exploring fluorescence quenching.

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Monitoring the charge-transfer process in a Nd-doped semiconductor based on photoluminescence and SERS technology.

Influence of ultrasound power on acoustic streaming and micro-bubbles formations in a low frequency sono-reactor: Mathematical and 3D computational simulation

We propose a simple and compact reading head with the Littrow configuration that will increase measurement range and reduce the complexity of a two-dimensional grating-based interferometer. The reading head contains only a beam splitter, two polarizing beam splitter modules, and two mirrors. The theoretical resolutions in two directions are 0.27 nm and 0.18 nm, respectively. In comparison with a dual-frequency laser interferometer, the proposed interferometer can measure displacement from 3 nm to 10 mm with high accuracy. The 3σ values in two directions for the difference are 1.67 nm and 1.35 nm for a displacement of 9 nm. Repeatability for a displacement of 1 μm is better than 2 nm.

Simple and compact grating-based heterodyne interferometer with the Littrow configuration for high-accuracy and long-range measurement of two-dimensional displacement.

Numerical simulation of ultrasonic enhancement on mass transfer in liquid-solid reaction by a new computational model.

Numerical simulation of ultrasonic enhancement by acoustic streaming and thermal effect on mass transfer through a new computation model

Spatial heterodyne Raman spectroscopy is a spectroscopic detection technique that is particularly suitable for Raman measurements. The spectral range of traditional spatial heterodyne Raman spectrometer (SHRS) is limited by its spectral resolution and the number of detector elements. We propose an SHRS with an echelle-mirror structure that employs multiple diffraction orders to achieve a broad spectral coverage and high spectral resolution simultaneously. This SHRS is used to obtain the Raman spectra of organic liquids, inorganic solid targets, and mixed targets. Observations of aqueous solutions, and minerals are presented. In addition, anti-Stokes Raman shifts are also presented. The proposed SHRS technique shows good performance for broadband, high-resolution Raman measurements.

Development of a spatial heterodyne Raman spectrometer with echelle-mirror structure.

A spectral reduction algorithm for an echelle spectrometer with spherical mirrors that builds a one-to-one correspondence between the wavelength and pixel position is proposed. The algorithm accuracy is improved by calculating the offset distance of the principal ray from the center of the image plane in the two-dimensional vertical direction and compensating the spectral line bending from the reflecting prism. The simulation and experimental results verify that the maximum deviation of the entire image plane is less than one pixel. This algorithm ensures that the wavelengths calculated from spectrograms have a high spectral resolution, meaning the precision from the spectral analysis reaches engineering standards of practice.

Bayanheshig

Papers

Simple and compact grating-based heterodyne interferometer with the Littrow configuration for high-accuracy and long-range measurement of two-dimensional displacement.

Numerical simulation of ultrasonic enhancement on mass transfer in liquid-solid reaction by a new computational model.

Numerical simulation of ultrasonic enhancement by acoustic streaming and thermal effect on mass transfer through a new computation model

Development of a spatial heterodyne Raman spectrometer with echelle-mirror structure.

High-accuracy spectral reduction algorithm for the échelle spectrometer.