Vibrational Imaging Research Articles

Stimulated Raman Excited Fluorescence Spectroscopy of Visible Dyes.

Fluorescence spectroscopy and Raman spectroscopy are two major classes of spectroscopy methods in physical chemistry. Very recently, stimulated Raman excited fluorescence (SREF) has been demonstrated ( Xiong, H.; et al. Nature Photonics , 2019 , 13 , 412 - 417 ) as a new hybrid spectroscopy that combines the vibrational specificity of Raman spectroscopy with the superb sensitivity of fluorescence spectroscopy (down to the single-molecule level). However, this proof-of-concept study was limited by both the tunability of the commercial laser source and the availability of the excitable molecules in the near-infrared. As a result, the generality of SREF spectroscopy remains unaddressed, and the understanding of the critical electronic preresonance condition is lacking. In this work, we built a modified excitation source to explore SREF spectroscopy in the visible region. Harnessing a large palette of red dyes, we have systematically studied SREF spectroscopy on a dozen different cases with a fine spectral interval of several nanometers. The results not only establish the generality of SREF spectroscopy for a wide range of molecules but also reveal a tight window of proper electronic preresonance for the stimulated Raman pumping process. Our theoretical modeling and further experiments on newly synthesized dyes also support the obtained insights, which would be valuable in designing and optimizing future SREF experiments for single-molecule vibrational spectroscopy and supermultiplex vibrational imaging.

Addendum: Vibrational spectroscopic image analysis of biological material using multivariate curve resolution-alternating least squares (MCR-ALS).

Addendum: Vibrational spectroscopic image analysis of biological material using multivariate curve resolution-alternating least squares (MCR-ALS).

Exploring Vibration Transmission Rule of an Artificial Spider Web for Potential Application in Invulnerability of Wireless Sensor Network.

Significant similarities exist between a spider web and wireless sensor network in terms of topology. Combining the unique advantages of the spider web in nature, such as invulnerability and robustness, with communication technology of a wireless sensor network presents high research value and broad development prospects. In this paper, a sort of a spiral artificial spider web based on 3D printing and its associated vibration testing device is proposed, which is used to study the transmission rule of vibration information of the spider web under given excitation conditions. It provides useful inspiration for establishment of an invulnerable communication rule of wireless sensor network. In order to investigate vibration transmission characteristics of the artificial spider web, vibration images are recorded and analyzed by a high-speed photography system, and vibration intensity is characterized by use of peak-to-peak value. Furthermore, vibration performance of the artificial spider web is studied under conditions of integrity and destruction, respectively. Our test observation reveals the vibration transmission rule of the unique structure of the spider web, providing a novel analysis method for improving invulnerability of the wireless sensor network.

EFFECT OF MUSCLE ENERGY TECHNIQUE IN CHRONIC SACROILIAC JOINT DYSFUNCTION

Objective: The study conducted for evaluating the effectiveness of muscle energy technique in chronic SIJ dysfunction. Methods: 30 patients with chronic sacroiliac joint dysfunction from both genders. Patients were divided into 2 groups 15 in each group .Group A: received muscle energy technique using post isometric relaxation technique to erector spinae, hamstrings, iliopsoas and quadratus lumborum plus conventional treatment program. Group B: control group received conventional treatment program only .Doppler imaging of vibration, palpation meter and visual analogue scale were utilized for evaluating patients (pre and post treatment). Results: The study findings revealed a statistical significant decrease of anterior pelvic tilting angle in group A (p<0.001), also a significant decrease of pain in the 2 groups compared with pre-intervention values(p<0.001) . Conclusion: Muscle energy technique is an effective treatment for decreasing anterior pelvic tilting angle and reducing pain in patients with chronic sacroiliac joint dysfunction. Key words: Muscle energy technique, Doppler imaging of vibration. Palpation meter.

Fracture Mechanism Analysis and Structural Improvement for 1000-kV UHV Shield Ring

Some fracture failures of multiple shield rings on a 1000-kV ultra-high voltage transmission line have been found in succession. The method of reinforcing and welding at the fracture site were used to avoid crack enlargement. However, the reinforced shield rings were damaged again after half a year's use. A new approach is proposed to extract the root cause. The finite-element method is employed to calculate the static performance of shield ring for determining that the cause of the crack is not the ultimate strength failure of the material. And after acquiring the wind vibration frequency by vibration image recognition method, the critical vibration wind speed is obtained by the vortex-induced resonance analysis. And based on the critical speed, the lift force function is formed. According to the historical load simulated by lift force function, the displacement and stress response under the vortex-induced resonance are acquired by transient dynamic calculation. With the regional meteorological data of the transmission line, the probability of the wind direction and velocity within the critical vibration wind speed range is calculated out. Then, with the probability, the displacement and stress response and the vibration frequency of shield ring, the fatigue life assessment is conducted. Inspired by the idea of the energy dissipation-seismic reduction, a new type shield ring is designed. After testing the mechanical and electrical performance, the new one runs perfectly without emerging crack from November 2016, that verified the effectiveness of the design scheme for the new type shield ring.

Behavioral Tracking and Neuromast Imaging of Mexican Cavefish.

Cave-dwelling animals have evolved a series of morphological and behavioral traits to adapt to their perpetually dark and food-sparse environments. Among these traits, foraging behavior is one of the useful windows into functional advantages of behavioral trait evolution. Presented herein are updated methods for analyzing vibration attraction behavior (VAB: an adaptive foraging behavior) and imaging of associated mechanosensors of cave-adapted tetra, Astyanax mexicanus. In addition, methods are presented for high-throughput tracking of a series of additional cavefish behaviors including hyperactivity and sleep-loss. Cavefish also show asociality, repetitive behavior and higher anxiety. Therefore, cavefish serve as an animal model for evolved behaviors. These methods use free-software and custom-made scripts that can be applied to other types of behavior. These methods provide practical and cost-effective alternatives to commercially available tracking software.

Characterization of supercontinuum generation in a photonic crystal fiber for uses in multiplex CARS microspectroscopy

AbstractCoherent anti‐Stokes Raman scattering (CARS) is a versatile technique for vibrational imaging that can be realized by a simple setup using a single femtosecond laser oscillator. For such a layout, supercontinuum generation in a photonic crystal fiber (PCF) is commonly used to produce a broadband Stokes beam in the so‐called multiplex CARS spectroscopy; accordingly, characterization of the supercontinuum beam is a necessary requirement to perform controlled experiments. In this paper, we first perform simulations and characterizations of the supercontinuum spectra produced by a PCF in conditions encountered in a typical single‐oscillator multiplex CARS setup. Good agreement between the experimental and simulated supercontinuum spectra is obtained in the whole emission band and for different PCF working conditions, by accurate choice of the simulation input parameters and by accounting for the input beam chirp in the numerical code. The influence of PCF working conditions on the CARS signal measured on a reference sample is also shown. To this regard, we also study the long‐term stability of the Stokes beam and of the associated CARS signal, using the Allan variance to determine a limit to the acquisition time in CARS measurements. We show that Stokes and CARS long‐term spectral fluctuations are on a timescale of some minutes in our setup, setting an indicative limit to the practical acquisition time for reliable CARS measurements. Based on this work, good control over the measurement of vibrational bands by CARS microscopy can be achieved in view of optimized performances in specific spectral bands.

Saturated Stimulated-Raman-Scattering Microscopy for Far-Field Superresolution Vibrational Imaging

Superresolution microscopy based on stimulated Raman scattering (SRS) is appealing for label-free quantitative imaging of biological and biomedical systems with higher resolution than conventional SRS microscopy, which is diffraction-limited. This study experimentally demonstrates a saturated SRS (SSRS) technique to break the diffraction limit for vibrational imaging of biological samples, such as chloroplasts and Hela cells. The technique holds great promise for studying living cells.

Abstract P6-01-03: Exploring the relationship between an in vitro model of breast cancer cell mineralisation and the cancer grade specific composition of ex vivo microcalcifications

Abstract Background: Microcalcifications resulting from calcium deposition in the mammary gland play a central role in the early detection of breast cancer [1]. However, the relationship between their occurrence in the breast and cancer progression remains poorly understood. Our approach is to use vibrational spectroscopy and imaging, which is non-invasive, non-destructive, label-free and chemically specific, to assess the composition and distribution of the deposits in an in vitro cancer cell model of mineralisation [2]. In parallel we will utilise the same methods to measure the biochemical composition of microcalcifications found in breast biopsies from different grades of cancer. The ultimate aim of the study is to link the changes identified during the in vitro mineralisation process with the different stages of breast cancer. Vibrational spectroscopic methods can provide incredibly detailed biomolecular fingerprints enabling us to elucidate both the compositional changes with advancing pathology and the spatial distribution of those changes within the calcification and the surrounding tissue. Methods: The breast cancer cell line MDA-MB-231 has the ability to produce mineralisation. This mineralisation was assessed over a 14-day period in the presence of different osteogenic cocktails: one composed of ascorbic acid, β-glycerophosphate (βG) and dexamethasone (Dex), and another one composed of inorganic phosphate (Pi). Fixed cells were analysed using Raman spectroscopy and micro-FTIR imaging at different time points (3, 7, 11 and 14 days). Tissue sections from patients with microcalcifications identified in histopathology will be sectioned to 3 mm and imaged with infrared (Agilent 670 FTIRinterferometer and Focal Plane Array imaging microscope) and Raman (Renishaw inVia) microspectrometers. Results: We observed distinct and specific phosphate peak (PO43-) at 960 and 1020 cm-1 in Raman and FTIR spectra, respectively, corresponding to hydroxyapatite crystal and indicating the presence of microcalcification formation. Treatment with Pi induced a faster mineralisation (day 3) compared to cells treated with βG (day 11) and different spectral profiles during this development phase. In addition, there are changes in both the relative DNA and protein concentrations in the cells following 11 days exposure to the osteogenic agents. It has been shown that the level of carbonate substitution in the calcium hydroxyapatite crystal correlates directly with the pathology of the tissue surrounding the microcalcification. Here we compare the mineral composition found ex vivo versus the in vitro model. Conclusion: It could be possible to link the progressive biophysical changes associated with mineralisation to distinct stages of breast cancer pathology based on protein, lipid and carbonated apatite contents of the mineralised cells. Support:This work was conducted as part of the Marie Curie Innovative Training Network Mid-TECH [H2020-MSCA-ITN-2014-642661]

Fault Diagnosis of Active Magnetic Bearing⁻Rotor System via Vibration Images.

As important sources in fault diagnosis of rotary machinery, vibration signals are usually processed in the time or frequency domain as features to distinguish different classes of faults. However, these kinds of processing methods always ignore the corresponding relations among multiple signals, resulting in information loss. In this paper, a new fault description strategy named vibration image is proposed, based on which three new kinds of features are extracted, containing coupling information between different channels of vibration signals. Additionally, a new feature fusion method called two-layer AdaBoost is designed to train the fault recognition model, which avoids overfitting when the dataset is not large enough. Features based on vibration images combined with two-layer AdaBoost are adopted to diagnose faults of rotary machinery. Taking an active magnetic bearing-rotor system as the experimental platform, a dataset with four classes of faults is collected and our algorithm achieves good performance. Meanwhile, features based on vibration images and two-layer AdaBoost are both proved to be efficient separately.

Terahertz coherent anti-Stokes Raman scattering microscopy

Vibrational spectroscopic imaging is useful and important in biological and medical studies. Yet, vibrational imaging in the terahertz region (<300 cm−1) under biologically relevant conditions is currently unavailable, as none of the available methods possesses a sufficient sensitivity and high spatial resolution at the same time. Here, we develop a terahertz coherent anti-Stokes Raman scattering (THz-CARS) microscope with a high sensitivity and high spatial resolution that shows chemically selective imaging of biological tissues by using low-frequency collective modes of the corresponding constituents, filling the existing energy scale gap for vibrational imaging in the THz region. The observation of collective modes of biomacromolecules, such as collagen and non-collagenous proteins, may have significant implications for elucidating their corresponding biological functions, and the methodology presented may find wider applications in biomedical research.

Sum Frequency Generation Imaging Microscopy of Self-Assembled Monolayers on Metal Surfaces: Factor Analysis of Mixed Monolayers

Sum frequency generation (SFG) images of microcontact patterned self-assembled alkanethiol monolayers on metal surfaces were analyzed by factor analysis (FA) to determine the spatial distribution of the patterned monolayers over the images. Additionally, each significant abstract factor produced by FA was assessed to determine the information contained within it. These results indicate that FA of the SFG spectra is a promising method to determine the composition and identities of mixed alkanethiol systems that show different vibrational spectra and image contrast. Factor analysis has successfully been applied to SFG images obtained with low signals, which reduces the time required for full spectral SFG imaging.

Acquisition of meshing vibration data and image pictures of crack propagation at tooth root of plastic gears

Acquisition of meshing vibration data and image pictures of crack propagation at tooth root of plastic gears

Photonic Time-Stretch Spectroscopy for Multiplex Stimulated Raman Scattering

Stimulated Raman scattering spectroscopy enables label-free molecular identification, but its broadband implementation is technically challenging. We experimentally demonstrate a novel approach to multiplex stimulated Raman scattering based on photonic time stretch. A telecom fiber stretches the broadband femtosecond Stokes pulse after the sample to ∼15ns, mapping its spectrum in time. The signal is sampled through a fast oscilloscope, providing single-shot spectra at 80-kHz rate. We demonstrate high sensitivity in detecting the Raman vibrational modes of various samples over the entire high-frequency C-H stretching region. Our results pave the way to high-speed broadband vibrational imaging for materials science and biophotonics.

A Proposal of Vibration Imaging Method for Vibrating Objects with Translation

A Proposal of Vibration Imaging Method for Vibrating Objects with Translation

Bearing Fault Diagnosis under Variable Rotational Speeds Using Stockwell Transform-Based Vibration Imaging and Transfer Learning

In this paper, discrete orthonormal Stockwell transform (DOST)-based vibration imaging is proposed as a preprocessing step for supporting load and rotational speed invariant scenarios for signals of various health conditions. For any health condition, features can easily be extracted from its generated health pattern. To automate the feature selection process, a convolutional neural network (CNN)-based transfer learning (TL) approach for diagnosis has also been introduced. Transfer learning allows an established model to use feature knowledge obtained under one set of working conditions through hidden layers to diagnose faults that occur under other working conditions. The network learns from the massive source dataset, and that knowledge is applied to the target data to identify faults. Using the bearing dataset of Case Western Reserve University, the proposed approach yields an average 99.8% classification accuracy and, specifically, 99.99% for healthy condition (HC), 99.95% for inner race fault (IRF), 99.96% for ball fault (BF), 99.68% for outer race fault for 12 o’clock sensor position (ORF@12), 99.93% for outer race fault for 3 o’clock sensor position (ORF@3), and 99.89% for outer race fault for 6 o’clock sensor position (ORF@6). In this paper, the proposed approach is compared with conventional artificial neural networks (ANNs), support vector machines (SVMs), hierarchical CNNs, and deep autoencoders. The proposed approach outperforms these conventional methods in the accuracy under all working conditions.

Supercritical focusing coherent anti-Stokes Raman scattering microscopy for high-resolution vibrational imaging.

We report the development of, to the best of our knowledge, a novel supercritical focusing coherent anti-Stokes Raman scattering (SCF-CARS) microscopy for high-resolution vibrational imaging. Two optimized phase patterns with a combination of concentric rings with an alternative 0 and π phase are generated by using a spatial light modulator and applied to the pump beam for minimizing its focal spot size. One of the phase patterns is for both the lateral and axial resolution enhancement, and the other can further improve the lateral resolution, but it sacrifices the axial resolution to some extent. We demonstrate this high-resolution SCF-CARS microscopy technique by imaging the polymethyl methacrylate (PMMA) nano-cylinder on a microscope slide and glass-air interface, as well as biomedical samples, for example, tooth.

Femtosecond Vibrational Sum-Frequency Generation Spectroscopy of Chiral Molecules in Isotropic Liquid.

Vibrationally resonant optically active (VOA) sum-frequency generation (SFG) is a second-order nonlinear process sensitive to the stereospecific vibrational structure of chiral molecules. We demonstrate that a femtosecond VOA SFG signal can be measured in the isotropic bulk of a chiral liquid. The chiral, achiral, and VOA SFG spectra of R- and S-limonene and their racemic mixture in the C-H stretching frequency region are characterized. In particular, it is shown that the observed circular intensity difference (CID) signal, which can provide distinguishable stereochemical vibrational information between enantiomers, arises from interference of the electric-dipole allowed antisymmetric Raman tensor-induced and Raman optical activity (ROA) tensor-induced SFG fields. Furthermore, we show that the CID and linear polarization intensity difference (LID) SFG spectra are connected to the real and imaginary parts of the effective chiral VOA SFG susceptibility, respectively. We anticipate that the present technique will be of use in transient chiroptical spectroscopy and stereochemical vibrational imaging studies.

Mapping the phase and amplitude of ossicular chain motion using sound-synchronous optical coherence vibrography.

The sound-driven vibration of the tympanic membrane and ossicular chain of middle-ear bones is fundamental to hearing. Here we show that optical coherence tomography in phase synchrony with a sound stimulus is well suited for volumetric, vibrational imaging of the ossicles and tympanic membrane. This imaging tool - OCT vibrography - provides intuitive motion pictures of the ossicular chain and how they vary with frequency. Using the chinchilla ear as a model, we investigated the vibrational snapshots and phase delays of the manubrium, incus, and stapes over 100 Hz to 15 kHz. The vibrography images reveal a previously undescribed mode of motion of the chinchilla ossicles at high frequencies.

Transient vibration imaging with time-resolved synthetic holographic confocal microscopy.

We introduce a new modality for dynamic phase imaging in confocal microscopy based on synthetic optical holography. By temporal demultiplexing of the detector signal into a series of holograms, we record time-resolved phase images directly in the time domain at a bandwidth as determined by the photo detector and digitizer. We demonstrate our method by optical imaging of transient vibrations in an atomic force microscope cantilever with 100 ns time resolution, and observe the dynamic deformation of the cantilever surface after excitation with broadband mechanical pulses. Temporal Fourier transform of a single data set acquired in 4.2 minutes yields frequency and mode profile of all excited out-of-plane vibration modes with sub-picometer vertical sensitivity and sub-micrometer lateral resolution. Our method has the potential for transient and spectroscopic vibration imaging of micromechanical systems at nano-and picosecond scale time resolution.