Circular Dichroism Spectral Similarity Plots to Extend Validation and Correction to All Measured Wavelengths

Interlaboratory comparisons of circular dichroism (CD) spectra are useful for developing confidence in the measurements associated with optically active molecules. These measurements also help define the higher-order (secondary and tertiary) structure of biopolymers. Unfortunately, the extent of the validity of these measurements has been unclear. In this work, a method is described to extend CD validation over the entire observed wavelength range using what will be called spectral similarity plots. The method involves plotting, wavelength by wavelength, all measured spectral intensities of a sample at one concentration against the intensity values of the same material at a different concentration or pathlength. These spectral similarity plots validate the instrument in terms of spectral shape and whether the shape is shifted in intensity and/or in wavelength. This comparison tests the linearity of instrument’s signal, the balance of its left and right polarizations, its wavelengths, and its spectral intensity scales. When the process is applied to materials with accepted and archived intensity values, the method can be linked to older single-wavelength and double-wavelength calibration techniques. Further, spectral similarity testing of CD spectra from samples with different concentrations run in different labs suggests that improved interlaboratory validation of CD data is possible. Since a database of archival CD measurements is available online, spectral similarity comparisons could possibly provide the ability to compare linearity, polarization balance, wavelength, and spectral intensity between all current CD instruments. If the preliminary results published here prove robust and transferable, then comparisons of full-wavelength range spectra to archived data using spectral similarity plots should become part of the standard process to validate and calibrate the performance of CD instruments.

Running Safety Assessment of Trains on Bridges under Earthquakes Based on Spectral Intensity Theory

The main goal of this paper is to perform the safety assessment of high-speed trains (HSTs) on the simply supported bridges (SSBs) under low-level earthquakes, which are frequently encountered by HSTs, utilizing spectral intensity (SI) index. First, the HST’s limit displacements, which are calculated by using the multi-body train model with detailed wheel–rail relationship, varying with train speed, frequency and amplitude of a sinusoidal base excitation are obtained. Then, based on the obtained HST’s limit displacements, the spectral intensity limits (SIL) graded by the train’s running speed are calculated, and the relationship between the bridge seismic dynamic responses and the train’s running safety was established. Next, the method that utilizes the SI and the SIL indexes to evaluate the HST’s running safety was proposed and verified by comparing with the evaluation result of the train–track–bridge interaction model. Based on the proposed SI index, the HST’s running safety on the SSBs was evaluated under earthquakes, considering different pier heights and site types. The results showed that the low-frequency components of the ground motions are unfavorable to the HST’s running safety, and the height of bridge piers has a significant impact on running safety.

Generation of Ultrabroad and Intense Supercontinuum in Mixed Multiple Thin Plates

Supercontinuum (SC) generation using multiple thin plates is demonstrated with a femtosecond laser pulse. We propose an improved technique to obtain larger spectrum broadening and higher spectral intensity by employing mixed multiple thin plates with different thicknesses and materials. Furthermore, the spectrum has good stability, which is superior to that of the spectrum induced by the traditional single filament in bulk material. Our approach offers a route towards simple and stable SC generation for potential applications.

Investigation of Fluconazole Susceptibility to Candida Albicans by MALDI-TOF MS and Real-Time PCR for CDR1, CDR2, MDR1 and ERG11

Background C. albicans is the most important yeast that caused the infection in humans; the trend of resistance to fluconazole (FLC) was also increased, while the FLC susceptibility by conventional method takes time causing the treatment failure. To investigate FLC susceptibility to C. albicans using MALDI-TOF MS and Real-time PCR for CDR1, CDR2, MDR1 and ERG11, overall, 32 C. albicans strains included 4 reference strains (3 FLC susceptible (S) and 1 FLC resistant (R), 1 spontaneous mutant strain (FLC susceptible-dose dependent, SDD) and 27 clinical strains obtained from 2 Thai University Hospitals were performed FLC susceptibility testing by Sensititre YeastOne and broth microdilution method, FLC resistant expression mechanism by Real-time PCR and the major peak determination by MALDI-TOF MS.Results The change of CDR1 and CDR2 mRNA expression were only significantly observed in SDD and R strains. Using MALDI-TOF MS, the change of mass spectral intensity at range 3376-3382 m/z (major peak) was significantly related to FLC susceptibility as SDD (decreased at 4 µg/ml and increase at 8 µg/ml), S (all increased), and R (all slightly decreased or no change) after incubation for 6 h. All 27 clinical strains showed FLC MIC susceptible (MIC range 0.25-2 µg/ml), no change in CDR1 and CDR2 expression and S major peak type. The FLC resistance C. albicans with CDR1 and CDR2 expression may possibly effect the change of mass spectral intensity at range 3376-3382 m/z. Conclusions The MALDI-TOF MS may be used to simultaneously classify and predict FLC resistant C. albicans strains associated with CDR1 and CDR2 expression. Further studies are essential to clarify the methodology and improve the reliability of this assay for routine diagnosis.

Classification of Aflatoxin B1 Concentration of Single Maize Kernel Based on Near-Infrared Hyperspectral Imaging and Feature Selection

A rapid and nondestructive method is greatly important for the classification of aflatoxin B1 (AFB1) concentration of single maize kernel to satisfy the ever-growing needs of consumers for food safety. A novel method for classification of AFB1 concentration of single maize kernel was developed on the basis of the near-infrared (NIR) hyperspectral imaging (1100–2000 nm). Four groups of AFB1 samples with different concentrations (10, 20, 50, and 100 ppb) and one group of control samples were prepared, which were preprocessed with Savitzky–Golay (SG) smoothing and first derivative (FD) algorithms for their raw NIR spectra. A key wavelength selection method, combining the variance and order of average spectral intensity, was proposed on the basis of pretreated spectra. Moreover, principal component analysis (PCA) was conducted to reduce the dimensionality of hyperspectral data. Finally, a classification model for AFB1 concentrations was developed through linear discriminant analysis (LDA), combined with five key wavelengths and the first three PCs. The results show that the proposed method achieved an ideal performance for classifying AFB1 concentrations in a single maize kernel with overall accuracy, with an F1-score and Kappa values of 95.56%, 0.9554, and 0.9444, respectively, as well as the test accuracy yield of 88.67% for independent validation samples. The combinations of variance and order of average spectral intensity can be used for key wavelength selection which, combined with PCA, can achieve an ideal dimensionality reduction effect for model development. The findings of this study have positive significance for the classification of AFB1 concentration of maize kernels.

Repeatability enhancing method for one-shot LIBS analysis via spectral intensity correction based on probability distribution

It is significant to improve the repeatability of quantitative analysis of laser-induced breakdown spectroscopy (LIBS) in one-shot measurement where the skill of averaging is not valid because multiple measurements are...

Aggregation-induced Chirality Amplification of Optically Active Fluorescent Polyurethane and Cyclic Dimer in the Ground and Excited States

Optically active linear polyurethane and cyclic dimer were synthesized from 2,7-diisocyanatofluorene and 2,2’-dihydroxy-1,1’-binaphthyl. Circular dichroism (CD) spectral intensity of polymer was amplified at a higher concentration through aggregate formation while...