Vibrational Imaging Research Articles

Vibrational Spectroscopic Analyses and Imaging of the Early Middle Ages Hemp Bast Fibres Recovered from Lake Sediments.

Fourier Transform Infrared (FT-IR) spectroscopy and imaging combined with hierarchical cluster analysis (HCA) was applied to analyse biochemical properties of Early Middle Ages hemp (Cannabis sativa L.) bast fibres collected from lake bottom sediment of lake Słone. The examined plant macrofossil material constitutes residues of the hemp retting process that took place in the 7th–8th century. By comparison of three samples: untreated isolated bast fibres, and fibres incubated overnight at 4 and 37 °C, we were able to mimic the retting conditions. Using FT-IR qualitative and semi-quantitative assessment of the primary polysaccharides content, total protein content, and their spatial distribution was performed within the hemp fibres. The concentration of cellulose remained vastly unchanged, while the concentration of lignin and pectin was the highest in the untreated sample. The spatial distributions of compounds were heterogeneous in the untreated and 4 °C-incubated samples, and homogenous in the specimen processed at 37 °C. Interestingly, a higher amide content was detected in the latter sample indicating the highest degree of enzymatic degradation. In this study, we show that the spectroscopic methods allow for a non-destructive evaluation of biochemical composition of plant fibres without preparation, which can be an appropriate approach for studying ancient plant remains.

A novel method for predicting delamination of carbon fiber reinforced plastic (CFRP) based on multi-sensor data

Carbon fiber reinforced plastic (CFRP) has been widely used in many fields such as in the aerospace and automotive industries. Drilling of CFRP is a key process in the manufacture of CFRP components. The existing quality control and tool change decision methods are mainly based on delamination damage. However, estimating delamination damage in situ is still a challenge in the process of continuous drilling. To solve this problem, a comprehensive delamination prediction method based on multi-sensor data is proposed in this paper. In process of the drilling, the force, torque, temperature, vibration and hole exit images were collected, and the delamination was quantified by a proposed statistical delamination factor Fs. Singular spectrum analysis (SSA) is used to smooth the Fs sequence to reduce randomness. Then, a XGBoost-ARIMA model is constructed for rolling prediction of Fs. Finally, drilling experiments were carried out to verify the effectiveness of the proposed method. The experimental results showed that compared with traditional delamination evaluation factors, Fs reduced the mean square error (MSE) of prediction by more than 50%. Compared with that of traditional machine learning models such as an SVM and ANN, the MSE of the model’s regression part is decreased by more than 39%. The proposed method can provide a solution for real-time and in situ prediction of delamination damage in the continuous drilling process of CFRP components.

A Combined Short Time Fourier Transform and Image Classification Transformer Model for Rolling Element Bearings Fault Diagnosis in Electric Motors

The most frequent faults in rotating electrical machines occur in their rolling element bearings. Thus, an effective health diagnosis mechanism of rolling element bearings is necessary from operational and economical points of view. Recently, convolutional neural networks (CNNs) have been proposed for bearing fault detection and identification. However, two major drawbacks of these models are (a) their lack of ability to capture global information about the input vector and to derive knowledge about the statistical properties of the latter and (b) the high demand for computational resources. In this paper, short time Fourier transform (STFT) is proposed as a pre-processing step to acquire time-frequency representation vibration images from raw data in variable healthy or faulty conditions. To diagnose and classify the vibration images, the image classification transformer (ICT), inspired from the transformers used for natural language processing, has been suitably adapted to work as an image classifier trained in a supervised manner and is also proposed as an alternative method to CNNs. Simulation results on a famous and well-established rolling element bearing fault detection benchmark show the effectiveness of the proposed method, which achieved 98.3% accuracy (on the test dataset) while requiring substantially fewer computational resources to be trained compared to the CNN approach.

Ultrasensitive Vibrational Imaging of Retinoids by Visible Preresonance Stimulated Raman Scattering Microscopy.

High‐sensitivity chemical imaging offers a window to decipher the molecular orchestra inside a living system. Based on vibrational fingerprint signatures, coherent Raman scattering microscopy provides a label‐free approach to map biomolecules and drug molecules inside a cell. Yet, by near‐infrared (NIR) pulse excitation, the sensitivity is limited to millimolar concentration for endogenous biomolecules. Here, the imaging sensitivity of stimulated Raman scattering (SRS) is significantly boosted for retinoid molecules to 34 micromolar via electronic preresonance in the visible wavelength regime. Retinoids play critical roles in development, immunity, stem cell differentiation, and lipid metabolism. By visible preresonance SRS (VP‐SRS) imaging, retinoid distribution in single embryonic neurons and mouse brain tissues is mapped, retinoid storage in chemoresistant pancreatic and ovarian cancers is revealed, and retinoids stored in protein network and lipid droplets of Caenorahbditis elegans are identified. These results demonstrate VP‐SRS microscopy as an ultrasensitive label‐free chemical imaging tool and collectively open new opportunities of understanding the function of retinoids in biological systems.

Mineralogical classification and crystal water characterisation of beryl from the W–Sn–Be occurrence of Xuebaoding, Sichuan province, western China

AbstractBeryl from Xuebaoding, Sichuan Province, western China is known for its unusual tabular habit and W–Sn–Be paragenesis in a greisen-type deposit. The crystals are typically colourless transparent to pale blue, often with screw dislocations of hexagonal symmetry on the (0001) crystal faces. Combining electron microprobe analyses and laser ablation inductively coupled plasma mass spectrometry with single-crystal X-ray diffraction (XRD), correlated with Raman and micro-infrared (IR) spectroscopy and imaging, the crystal chemical characteristics are determined. The contents of Na+ (0.24–0.38 atoms per formula unit (apfu)) and Li+ up to 0.38 apfu are at the high end compared to beryl from other localities worldwide. Li+ substitution for Be2+ on the tetrahedral (T2) site is predominantly charge balanced by Na+ on the smaller channel (C2) site, with Na+ ranging from 91.5% to 99.7% (apfu) of the sum of all other alkali elements. Cs+ and minor Rb+ and K+ primarily charge balance the minor M2+ substitution for Al3+ at the A site; all iron at the A site is suggested to be trivalent. The a axis ranges from 9.2161(2) to 9.2171(4) Å, with unit-cell volume from 678.03(3) to 678.48(7) Å3. The c/a ratio of 1.0002–1.0005 is characteristic for T2-type beryl with unit-cell parameters controlled primarily by Be2+ substitution. Transmission micro-IR vibrational spectroscopy and imaging identifies coordination of one or two water molecules to Na+ (type IIs and type IId, respectively) as well as alkali free water (type I). Based on IR absorption cross section and XRD a C1 site water content of 0.4–0.5 apfu is derived, i.e. close to 50% site occupancy. Secondary crystal phases with a decrease in Fe and Mg, yet increase in Na, suggest early crystallisation of aquamarine, with goshenite being late. With similar crystal chemistry to beryl of columnar habit from other localities worldwide, the tabular habit of Xuebaoding beryl seems to be unrelated to chemical composition and alkali content.

Психофизиологический экспресс-контроль лиц опасных профессий, управляющих системами вооружений

The article presents the relevance of the development of methods for rapid control of the psychophysiological state of persons of hazardous occupations (OP), managing weapons systems, and the tasks solved with their help. The issues of improving the system of psychophysiological support of the professional activities of military operators in order to increase their professional reliability and preserve professional health are considered. The technology of vibration imaging is described, which makes it possible to assess the psychophysiological state without contact and quickly (testing time – 1 min). Examples of its practical application in training and pre-shift psychophysiological control are given.

A Novel Method Based on UNET for Bearing Fault Diagnosis

Reliability of rotating machines is highly dependent on the smooth rolling of bearings. Thus, it is very essential for reliable operation of rotating machines to monitor the working condition of bearings using suitable fault diagnosis and condition monitoring approach. In the recent past, Deep Learning (DL) has become applicable in condition monitoring of rotating machines owing to its performance. This paper proposes a novel bearing fault diagnosis method based on the processing and analysis of the vibration images. The proposed method is the UNET model that is a recent development in DL models. The model is applied to the 2D vibration images obtained by transforming normalized amplitudes of the time-series vibration data samples into the corresponding vibration images. The UNET model performs pixel-level feature learning using the vibration images owing to its unique architecture. The results demonstrate that the model can perform dense predictions without any loss of label information, generally caused by the sliding window labelling method. The comparative analysis with other DL models confirmed the superiority of the UNET model which has achieved maximum accuracy of 98.91% and F1-Score of 99%.

Analysis of Spatial Vibration on Scanning Mirror Imaging Based on Frequency Filtering

In order to analyze the impact of multisource vibration on the imaging quality of aerospace optical payload during camera scanning, a dynamic imaging quality degradation model fused with satellite vibration filter templates is established. Firstly, according to the motion scanning process of the TDI camera, a filter template combining the amplitude and frequency of the vibration source is designed; Secondly, a piecewise function of satellite vibration with a frequency range of 1 Hz to 1000 Hz is obtained by curve fitting, and the amplitudes of different frequency ranges are brought into the image filter template to simulate the output image affected by the vibration. Finally, the output degraded image is analyzed through structural similarity and mean square error. The simulation results show that during the imaging process of the aerospace scanning mirror, the line frequency of the camera changes regularly with the scanning speed. When platform vibration frequency is similar to the camera’s exposure frequency, it will have a large impact on image quality. Therefore, when the camera’s exposure frequency is 110 Hz, vibration at a frequency of 110 Hz will further degrade the image quality. This article is expected to provide guidance for spatial vibration suppression and image quality degradation assessment in the imaging process of aerospace scanning mirrors.

<i>Vibration and Thermal Image Control Methods and Diagnostics of Rotary Equipment at </i> <i>OJSC "BSW - Management Company of "BMC" Holding"</i>

<i>Vibration and Thermal Image Control Methods and Diagnostics of Rotary Equipment at </i> <i>OJSC "BSW - Management Company of "BMC" Holding"</i>

Multiplexed Fourier Transform Infrared and Raman Imaging.

Infrared (IR) and Raman spectroscopies are being increasingly employed for the label-free analysis of biochemical samples. Both are vibrational imaging techniques, but they provide complementary information about the chemical composition of the sample, and thus the integration of Raman and IR images leads to a comprehensive understanding of the samples. Here, we summarize the steps needed for performing multiplexed infrared and Raman imaging, identifying and overcoming the two main challenges: first, the technical difficulties caused by the incompatibilities of the techniques and, second, the necessity to extract the information from the large number of vibrational variables found in both IR and Raman spectra.

Label-free imaging of fibroblast membrane interfaces and protein signatures with vibrational infrared photothermal and phase signals.

Label-free vibrational imaging of biological samples has attracted significant interest due to its integration of structural and chemical information. Vibrational infrared photothermal amplitude and phase signal (VIPPS) imaging provide label-free chemical identification by targeting the characteristic resonances of biological compounds that are present in the mid-infrared fingerprint region (3 µm - 12 µm). High contrast imaging of subcellular features and chemical identification of protein secondary structures in unlabeled and labeled fibroblast cells embedded in a collagen-rich extracellular matrix is demonstrated by combining contrast from absorption signatures (amplitude signals) with sensitive detection of different heat properties (lock-in phase signals). We present that the detectability of nano-sized cell membranes is enhanced to well below the optical diffraction limit since the membranes are found to act as thermal barriers. VIPPS offers a novel combination of chemical imaging and thermal diffusion characterization that paves the way towards label-free imaging of cell models and tissues as well as the study of intracellular heat dynamics.

Combining the best of two worlds: Stimulated Raman excited fluorescence

The pursuit of a hybrid spectroscopy that combines the superb sensitivity of fluorescence and the high chemical specificity of Raman scattering has lasted for 40 years, with multiple experimental and theoretical attempts in the literature. It was only recently that the stimulated Raman excited fluorescence (SREF) process was successfully observed in a broad range of fluorophores. SREF allows single-molecule vibrational spectroscopy and imaging in the optical far field without relying on plasmonic enhancement. In this perspective, we will first review the historical efforts that lead to the successful excitation and detection of SREF, followed by the underlying physical principles, then the remaining technical challenges will be discussed, and, at last, the future opportunities in this old but yet newly emerged spectroscopy are outlined.

Label-free vibrational imaging of different A\u03b2 plaque types in Alzheimer\u2019s disease reveals sequential events in plaque development

The neuropathology of Alzheimer’s disease (AD) is characterized by hyperphosphorylated tau neurofibrillary tangles (NFTs) and amyloid-beta (Aβ) plaques. Aβ plaques are hypothesized to follow a development sequence starting with diffuse plaques, which evolve into more compact plaques and finally mature into the classic cored plaque type. A better molecular understanding of Aβ pathology is crucial, as the role of Aβ plaques in AD pathogenesis is under debate. Here, we studied the deposition and fibrillation of Aβ in different plaque types with label-free infrared and Raman imaging. Fourier-transform infrared (FTIR) and Raman imaging was performed on native snap-frozen brain tissue sections from AD cases and non-demented control cases. Subsequently, the scanned tissue was stained against Aβ and annotated for the different plaque types by an AD neuropathology expert. In total, 160 plaques (68 diffuse, 32 compact, and 60 classic cored plaques) were imaged with FTIR and the results of selected plaques were verified with Raman imaging. In diffuse plaques, we detect evidence of short antiparallel β-sheets, suggesting the presence of Aβ oligomers. Aβ fibrillation significantly increases alongside the proposed plaque development sequence. In classic cored plaques, we spatially resolve cores containing predominantly large parallel β-sheets, indicating Aβ fibrils. Combining label-free vibrational imaging and immunohistochemistry on brain tissue samples of AD and non-demented cases provides novel insight into the spatial distribution of the Aβ conformations in different plaque types. This way, we reconstruct the development process of Aβ plaques in human brain tissue, provide insight into Aβ fibrillation in the brain, and support the plaque development hypothesis.

Near-infrared double-illumination optical-resolution photoacoustic microscopy.

Label-free chemical bond imaging is of great importance in biology and medicine. Photoacoustic imaging at the third near-infrared windows (1600-1870 nm, near-infrared-III) provides a stable molecular vibrational imaging tool for lipid-rich tissue owing to the first overtone transition of the CH bond at 1.7 μm. However, lacking high-energy pulsed laser sources at 1.7 μm and the strong water absorption significantly limit the signal-to-noise ratio of the lipid imaging, especially for thin lipid tissues. To circumvent this barrier, we develop near-infrared-III double-illumination optical-resolution photoacoustic microscopy (DIOR-PAM) for improving the sensitivity of label-free lipid imaging. Using the same laser, DIOR-PAM can enhance the sensitivity by nearly 100%, which we prove in the Monte Carlo simulation. We experimentally demonstrated 50% ~ 100% sensitivity enhancements on nonbiological and biological lipid-rich samples.

Multimodal Imaging Based on Vibrational Spectroscopies and Mass Spectrometry Imaging Applied to Biological Tissue: A Multiscale and Multiomics Review.

Multimodal Imaging Based on Vibrational Spectroscopies and Mass Spectrometry Imaging Applied to Biological Tissue: A Multiscale and Multiomics Review.

Introduction to Infrared and Raman-Based Biomedical Molecular Imaging and Comparison with Other Modalities.

Molecular imaging has rapidly developed to answer the need of image contrast in medical diagnostic imaging to go beyond morphological information to include functional differences in imaged tissues at the cellular and molecular levels. Vibrational (infrared (IR) and Raman) imaging has rapidly emerged among the molecular imaging modalities available, due to its label-free combination of high spatial resolution with chemical specificity. This article presents the physical basis of vibrational spectroscopy and imaging, followed by illustration of their preclinical in vitro applications in body fluids and cells, ex vivo tissues and in vivo small animals and ending with a brief discussion of their clinical translation. After comparing the advantages and disadvantages of IR/Raman imaging with the other main modalities, such as magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography/single-photon emission-computed tomography (PET/SPECT), ultrasound (US) and photoacoustic imaging (PAI), the design of multimodal probes combining vibrational imaging with other modalities is discussed, illustrated by some preclinical proof-of-concept examples.

High‐sensitivity impulsive stimulated Raman spectrometer with fast data acquisition

AbstractImpulsive stimulated Raman scattering (ISRS) is a nonlinear coherent technique for the measurement of the vibrational spectrum of samples within the bandwidth of the excitation laser pulse, which, for pulse durations of several tens of femtoseconds, translates into easy access to the low‐wavenumber Raman spectrum (below few hundreds of cm−1). Recently, a degenerate ISRS Fourier‐transform Michelson spectrometer for measurements in bulk, transparent liquids operating with a single, nonamplified femtosecond laser source, was demonstrated, although with low measurement speed, exploiting a position‐sensitive detector to measure the time evolution of the tiny spectral asymmetries of the probe beam produced by stimulated Raman gain and loss. Building on this innovation of the detection method, in this work, we show that using a different data acquisition concept, based on the fast modulation of the delay in one of the spectrometer arms, it is possible to measure scattering and absorbing samples in a much shorter time, approaching the real‐time visualization of the Raman spectrum of the sample under analysis. Furthermore, the setup described here does not suffer from creation of microbubbles, heating effects or thermal instabilities produced in the sample by increasingly high excitation fluences, and is therefore suitable to be implemented in vibrational microscopy applications with tight beam focusing. Thus, the present work is a contribution toward practical implementation of low‐wavenumber vibrational imaging, which is of importance for studies of intramolecular vibrational modes of large molecules or of heavy functional groups or for the study of intermolecular force constants in biological and nanostructured materials.

Electronic controlled optical activity analysis on NLO crystal; 4-Amino-5-Nitroindole using morphological, spectroscopic and theoretical tools

The organic NLO crystal for 4-Amino-5-Nitroindole was grown using slow evaporation method along with customized orthorhombic lattice formation and the crystal superiority was evaluated by recording XRD pattern. The framing of crystal structure using molecular planes was examined to find unit cell parameters. The space group (Pnam) for present organic molecular structure was assigned and the density of molecular structure in crystal geometry was measured using B3LYP/6–311++G (d,p). The electronic assisted optical activity of dielectric phase of material was tested and thereby efficiency of NLO activity was calculated. The organic composite geometry was clearly tested to find the molecular stacking and crystal density for stabilizing dielectric slabs. The mulliken charge domain displacement was traced and the parametric oscillation was studied for finding the crystal stabilization. The molecular cross-sectional scattering characteristics of base and allied bond network were studied from the vibrational analysis observation. The electrical assisted electronic process was examined for determining NLO activity to for test ultra-high frequency amplification. The CT complex was identified and it also found to be belonging to indole ring. The electronic and protonic depletion space was calculated from the result of molecular dipole moment and the static charge rigidity was acknowledged. The NBMO profile was keenly grafted and the transitional energy was measured at every consumed electronic energy bands. The vibrational circular dichroic enantiomer image at all vibrational regions was drafted and the sequential pattern of transmission and absorption was verified by obtained peak intensity.

Rapid imaging of tympanic membrane vibrations in humans.

Functional imaging of the human ear is an extremely challenging task because of its minute anatomic structures and nanometer-scale motion in response to sound. Here, we demonstrate noninvasive in vivo functional imaging of the human tympanic membrane under various acoustic excitations, and identify unique vibration patterns that vary between human subjects. By combining spectrally encoded imaging with phase-sensitive spectral-domain interferometry, our system attains high-resolution functional imaging of the two-dimensional membrane surface, within a fraction of a second, through a handheld imaging probe. The detailed physiological data acquired by the system would allow measuring a wide range of clinically relevant parameters for patient diagnosis, and provide a powerful new tool for studying middle and inner ear physiology.

Quantum-enhanced balanced detection for ultrasensitive transmission measurement

Balanced detection is a popular method to cancel out the effect of laser intensity noise in optical measurements and spectroscopy. However, the signal-to-noise ratio (SNR) that can be achieved with balanced detection is constrained by the standard quantum limit (SQL). Here, we propose quantum-enhanced balanced detection (QBD), which allows us to improve the SNR beyond the SQL to realize ultrasensitive transmission measurement. In QBD, squeezed vacuum is injected to one of the input ports of a beamsplitter (BS) used in balanced detection to produce a pair of light waves whose shot noises are entangled with each other. Compared with previous quantum-enhanced measurement methods, QBD is advantageous because it can handle a higher optical power without sacrificing the degree of sensitivity enhancement. We present the theory of QBD and discuss the effects of the splitting ratio of the BS and the optical loss caused by the sample under test. We also describe the application of QBD to the sensitivity enhancement of molecular vibrational imaging based on stimulated Raman scattering microscopy.