Quantitative fat analysis of milk using a line-illumination spatially offset Raman probe through carton packaging.

Milk is a popular dairy product that provides various nutrients, but consuming too much saturated fat from milk can increase the risk of diseases and obesity. Adulterated milk containing toxic substances can be harmful to human health, and toxic substances can enter the milk at any stage of production. Thus, analytical technologies for detecting various nutrients and harmful substances inside the package are a key requisite for the assessment of dairy products on the market. In this study, we developed a Raman spectroscopic method as a quantitative tool for assessing the milk fat composition and detecting toxic chemicals in packaged milk. Using a line-illumination deep Raman system based on both conventional optics and novel optical fibers, we could quantitatively discriminate the Raman signals of milk fat from those of the packaging materials. Finally, the present system allowed the detection of melamine in adulterated milk (employed as a toxicity model) using a multiple-depth fiber probe.

Multicolor-Raman analysis of Korean paintworks: emission-like Raman collection efficiency.

It has been reported that the scattering cross-sections of resonance Raman spectra strongly depend on the resonance between the laser's excitation energy and the electronic absorption band of pigments in solution. However, the actual collection of scattered photons is affected by diffuse scattering and self-absorption when studying painted colorants in artworks. Quantitative spectroscopic measurements are required to elucidate the apparent resonance Raman cross-sections in both solution and solid. In this study, we explored the excitation-dependent Raman scattering of natural and artificial Korean pigments painted on a wood block with six visible wavelengths. Our study shows that the Raman intensity profile agrees with the emission profile rather than with the absorption. We also assessed the validity of self-absorption and the outgoing resonance mechanism in the solid state for the results.

In situ real-time identification of packaged chemicals using a dual-offset optical probe.

In situ real-time and nondestructive identification of packaged chemicals is essential for applications such as homeland security and terrorism prevention. Although various Raman spectroscopic methods such as spatially offset Raman spectroscopy (SORS) and time-resolved Raman spectroscopy have been investigated for real-time detection, the background interference originating from packaging materials limits the accuracy of the analysis. In principle, the Raman background from the packaging cannot be removed completely. To overcome this limitation, we developed a SORS-based dual-offset optical probe (DOOP) system that offers real-time prediction of 20 chemicals concealed in various containers by completely removing the background signal. The DOOP system selectively acquires the Raman photons generated from both the outer packaging and the inner contents, whose intensities are dependent on the penetration depth of the laser. The Raman spectra obtained at two remote offsets are automatically subtracted after normalization. We demonstrate that the DOOP method provides the pure component spectra by completely removing background interference from three plastic containers for a total of 20 samples in three different containers. In addition, an artificial neural network (ANN) was applied to evaluate the accuracy of the real-time chemical identification system; our system led to drastic improvements of the ANN prediction accuracy.

Hyperspectral Raman Line Mapping as an Effective Tool To Monitor the Coating Thickness of Pharmaceutical Tablets.

Protective chemical coatings are deposited on drugs during the manufacturing process for the purpose of controlling the pharmacokinetics of active pharmaceutical ingredients (APIs). Although manufacturers attempt to coat all the tablets uniformly, the film thickness of an individual drug is statistically different and depends on the measuring position of the anisotropic structure, and analytical methods for measuring coating thickness must be robust to statistical and geometrical aberrations. Herein, we demonstrate that a spatially offset Raman-spectroscopy-based line mapping method offered excellent calibration and prediction of the coating thickness of 270 acetaminophen ( N-acetyl-para-aminophenol, paracetamol) tablets. Raman-scattered light resurfaced back from the coating and APIs, and offset-resolved spectra were projected according to the vertical positions in an imaging sensor. The Raman intensity ratio between the coating substance and the inner APIs is a key parameter in the analysis, and its variation with respect to the spatial offset is proportional to the coating thickness and duration. The results of this study have implications for the rapid spectroscopic thickness measurement of industrial products coated with transparent or translucent materials.

Hyperspectral depth-profiling with deep Raman spectroscopy for detecting chemicals in building materials.

Toxic chemicals inside building materials have long-term harmful effects on human bodies. To prevent secondary damage caused by the evaporation of latent chemicals, it is necessary to detect the chemicals inside building materials at an early stage. Deep Raman spectroscopy is a potential candidate for on-site detection because it can provide molecular information about subsurface components. However, it is very difficult to spectrally distinguish the Raman signal of the internal chemicals from the background signal of the surrounding materials and to acquire the geometric information of chemicals. In this study, we developed hyperspectral wide-depth spatially offset Raman spectroscopy coupled with a data processing algorithm to identify toxic chemicals, such as chemical warfare agent (CWA) simulants in building materials. Furthermore, the spatial distribution of the chemicals and the thickness of the building material were also measured from one-dimensional (1D) spectral variation.

Tuning 2D Light Upconversion Emission by Modulating Phonon Relaxation.

The photonic upconversion in rare earth atoms is widely used to convert "invisible" near infrared photons to "visible" photons with continuous wave light. By using a patterned substrate, upconversion become a route for creating new information-incorporating security codes. The amount of information in the cipher increases in proportion to the number of emission colors as well as the pattern structure. Subsequently, changing the chemical composition of upconversion phosphors on 2 D substrates is required to manufacture information-rich upconversion cryptography. In this study, we exploited temperature-controlled thermal reaction on upconversion films deposited on a quartz substrate to prepare security information codes. Multiple color emission was generated from upconversion films as the result of inserting high-frequency molecular oscillators into the film structures. Fourier-transform infrared (FTIR) and time-resolved study corroborated the mechanism of spectral variation of upconversion films.

Spectral evidence for multi-pathway contribution to the upconversion pathway in NaYF4:Yb3+,Er3+ phosphors.

Although upconversion phosphors have been widely used in nanomedicine, laser engineering, bioimaging, and solar cell technology, the upconversion luminescence mechanism of the phosphors has been fiercely debated. A comprehensive understanding of upconversion photophysics has been significantly impeded because the number of photons incorporated in the process in different competitive pathways could not be resolved. Few convincing results to estimate the contribution of each of the two-, three-, and four-photon channels of near-infrared (NIR) energy have been reported in yielding upconverted visible luminescence. In this study, we present the energy upconversion process occurring in NaYF4:Yb3+,Er3+ phosphors as a function of excitation frequency and power density. We investigated the upconversion mechanism of lanthanide phosphors by comparing UV/VIS one-photon excitation spectra and NIR multi-photon spectra. A detailed analysis of minor transitions in one-photon spectra and luminescence decay enables us to assign electronic origins of individual bands in multi-photon upconversion luminescence and provides characteristic transitions representing the corresponding upconversion channel. Furthermore, we estimated the quantitative contribution of multiple channels with respect to irradiation power and excitation energy.

Bis(4,4''-difluoro-1,1':3',1''-terphenyl-2'-carboxyl-ato-κO)tetra-kis-(methanol-κO)calcium methanol tetra-solvate.

In the title compound, [Ca(C(19)H(11)F(2)O(2))(2)(CH(3)OH)(4)]·4CH(3)OH, the Ca(2+) ion is located on an inversion centre and is hexa-coordinated by two O atoms of two 4,4''-difluoro-1,1':3',1''-terphenyl-2'-carboxyl-ate ligands and four O atoms of four methanol ligands, forming a CaO(6) polyhedron with a slightly distorted octa-hedral coordination geometry. The Ca-O-C angle between the carboxyl-ate group and the calcium ion is 171.8 (2)°. Two types of inter-molecular hydrogen-bond inter-actions (C=O⋯H and O-H⋯O) between the carboxyl-ate ligand, the methanol solvent mol-ecules and the coordinating methanol ligands generate a two-dimensional network parallel to (001).

Overexpression, crystallization and preliminary X-ray crystallographic analysis of pyridoxal biosynthesis lyase PdxS from Pyrococcus horikoshii.

Pyridoxal biosynthesis lyase (PdxS) is an important player in the biosynthesis of pyridoxal 5'-phosphate (PLP), the biologically active form of vitamin B(6). PLP is an important cofactor involved in the metabolic pathway of amine-containing natural products such as amino acids and amino sugars. PdxS catalyzes the condensation of ribulose 5-phosphate (Ru5P), glyceraldehyde 3-phosphate (G3P) and ammonia, while glutamine amidotransferase (PdxT) catalyzes the production of ammonia from glutamine. PdxS and PdxT form a complex, PLP synthase, and widely exist in eubacteria, archaea, fungi and plants. To facilitate further structural comparisons among PdxS proteins, the structural analysis of PdxS from Pyrococcus horikoshii encoded by the Ph1355 gene was initiated. PdxS from P. horikoshii was overexpressed in Escherichia coli and crystallized at 296 K using 2-methyl-2,4-pentanediol as a precipitant. Crystals of P. horikoshii PdxS diffracted to 2.61 Å resolution and belonged to the monoclinic space group P2(1), with unit-cell parameters a = 59.30, b = 178.56, c = 109.23 Å, ß = 102.97°. The asymmetric unit contained six monomers, with a corresponding V(M) of 2.54 Å(3) Da(-1) and a solvent content of 51.5% by volume.