Divided-aperture confocal Brillouin microscopy for simultaneous high-precision topographic and mechanical mapping.

Confocal Brillouin microscopy (CBM) is a novel and powerful technique for providing non-contact and direct readout of the micro-mechanical properties of a material, and thus used in a broad range of applications, including biological tissue detection, cell imaging, and material characterization in manufacturing. However, conventional CBMs have not enabled high precision mechanical mapping owing to the limited depth of focus and are subject to system drift during long-term measurements. In this paper, a divided-aperture confocal Brillouin microscopy (DCBM) is proposed to improve the axial focusing capability, stability, and extinction ratio of CBM. We exploit high-sensitivity divided-aperture confocal technology to achieve an unprecedented 100-fold enhancement in the axial focusing sensitivity of the existing CBMs, reaching 5 nm, and to enhance system stability. In addition, the dark-field setup improves the extinction ratio by 20 dB. To the best of our knowledge, our method achieves the first in situ topographic imaging and mechanical mapping of the sample and provides a new approach for Brillouin scattering applications in material characterization.

Divided-aperture subtraction-differential confocal method with nanoscale axial resolution.

In this paper, a divided-aperture subtraction-differential confocal method (DASDCM) is proposed to meet the requirements of nanoscale noncontact height measurements for precision machining, materials science, and biology. The DASDCM divides the spot on the detection focal plane into two groups of circular detection areas, which are symmetrical to the optical axis and consist of two concentric detection pinholes with different sizes in each group. Then, the DASDCM uses a subtraction of the intensity signals received from the two detection pinholes in each group to suppress the interference of the nonconjugated information on the intensity signal; it also uses the differential subtraction of two obtained circular detection signals to obtain a sensitive axial response curve. Thereby, the DASDCM greatly improves the axial resolution while considering the signal-to-noise ratio and axial dynamic range of the system and can realize surface height measurement without axial scanning by using the linear range of the axial response curve. Theoretical analysis and preliminary experiments show that DASDCM has an axial resolution of 2 nm with a laser wavelength of λ=632.8 nm and a numerical aperture of NA=0.8. It provides an effective technique for nanoscale height detection with high axial resolution.

Early metabolic characterization of brain tissues after whole body radiation based on gas chromatography-mass spectrometry in a rat model.

Radiation-induced brain injury involves acute, early delayed and late delayed damage based on the time-course and clinical manifestations. The acute symptoms are mostly transient and reversible, whereas the late delayed radiation-induced changes are progressive and irreversible. Therefore, evaluation of the organ-specific early response to ionizing radiation exposure is necessary for improving treatment strategies and minimizing possible damage at an early stage after radiation exposure. In the current study, the gas chromatography-mass spectrometry technique based on metabolomics coupled with metabolic correlation network was applied to investigate the early metabolic characterization of rat brain tissues following irradiation. Our findings showed that the metabolic response to irradiation was not just limited to the variations of individual metabolite levels, but also accompanied by alterations of network correlations among various metabolites. Metabolite clustering indicated that energy metabolism disorder and inflammation response were induced following radiation exposure. The correlation networks revealed that the strong positive correlations of differential metabolites were highly reduced and significant negative linkages were highlighted in irradiated groups even without statistical changes in metabolic levels. Our findings provided new insights into our understanding of the radiation-induced acute brain injury mechanism and clues as to the therapy target for clinical applications.

Three-dimensional resolution-enhancement divided aperture correlation-differential confocal microscopy with nanometer axial focusing capability.

Divided aperture confocal microscopy (DACM) provides an improved imaging depth, imaging contrast, and working distance at the expense of spatial resolution. Here, we present a new method-divided aperture correlation-differential confocal microscopy (DACDCM) to improve the DACM resolution and the focusing capability, without changing the DACM configuration. DACDCM divides the DACM image spot into two round regions symmetrical about the optical axis. Then the light intensity signals received simultaneously from two round regions by a charge-coupled device (CCD) are processed by correlation manipulation and differential subtraction to improve the DACM spatial resolution and axial focusing capability, respectively. Theoretical analysis and preliminary experiments indicate that, for the excitation wavelength of λ = 632.8 nm, numerical aperture NA = 0.8, and normalized offset vM = 3.2 of the two regions, the DACDCM resolution is improved by 32.5% and 43.1% in the x and z directions, simultaneously, compared with that of the DACM. The axial focusing resolution used for the sample surface profile imaging was also significantly improved to 2 nm.

Structural Integrity Assessment of an NEPE Propellant Grain Considering the Tension-Compression Asymmetry in Its Mechanical Property.

In order to investigate the effect of tension-compression asymmetry of propellant mechanical properties on the structural integrity of a Nitrate Ester Plasticized Polyether (NEPE) propellant grain, the unified constitutive equations under tension and compression were established, a new method for grain structural integrity assessment was proposed and the structural integrity of the NEPE propellant grain under the combined axial and transverse overloads was evaluated. The results indicate that the mechanical state of the NEPE propellant grain is in the coexistence of tension and compression under the combined axial and transverse overloads, and the tension and compression regions in the propellant grain is independent of the propellant constitutive behavior. The tension-compression asymmetry of the propellant mechanical properties has a certain impact on its mechanical response. The maximum equivalent stress and strain considering the tension-compression asymmetry falls between that obtained through the tension and compression constitutive model, and is the same as damage coefficient. The safety factor of the NEPE propellant grain considering the tension-compression asymmetry of its mechanical properties is larger than that non-considering, and the traditional method of structural integrity assessment is conservative.

Plasma metabolomic signatures from patients following high-dose total body irradiation.

Despite some advances in the study of radiation injuries, effective methods of prevention and treatment of severe acute radiation syndrome or illness (ARS) are still lacking. Therefore, an in-depth understanding of the biological characteristics associated with high dose radiation is essential to reveal the mechanisms underlying the varied biological processes following high dose radiation and the development of novel potent radioprotective agents. In the present study, plasma metabolic characteristics were investigated using hematopoietic stem cell transplantation patients (n = 36) undergoing total body ionizing irradiation (TBI) utilizing gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). Plasma was collected pre-irradiation, 3 days after completion of fractionated radiation therapy with a total dose of 12 Gy delivered at a dose rate of 8 cGy min-1. These metabolic disorders involve the dysregulation of the gut microflora, a shift in energy supply from aerobic respiration toward ketogenesis, protein synthesis and metabolism in response to TBI. Furthermore, the panel of four metabolic markers with most potential consisting of PC (O-38:5), urate, ornithine, and GCDCS for radiation injury was chosen by combining multiple methods of data processing that included univariate analysis, partial least squares discriminant analysis (PLS-DA), and multivariable stepwise linear regression analysis. While similar patterns of metabolic alterations were observed in patients of different genders, disease types and ages, specific changes were also found in specific patients following high doses of exposure. These findings provide valuable information for selecting metabolic biomarker panels for radiation injury, clues for radiation pathology and therapeutic interventions involved in high-dose radiation exposure.

Dataset on capability of suppressing background noise and anti-tilting of divided-aperture differential confocal Raman microscopy system.

The dataset describes the mechanism of suppressing the background noise of the divided-aperture differential confocal Raman microscopy system and the range of tilting angles that the system can handle. On the basis of the confocal microscopy (CM), the divided-aperture confocal microscopy divided the pupil plane of the objective lens into the illumination pupil and collection pupil. Compared with the CM, the divided-aperture confocal microscopy only changes the pupil parameters, according to the partially coherent imaging theory, we simulate and analyze the axial response curves of the divided-aperture confocal system and the traditional confocal system. We also simulated the differential confocal response curve at different tilting angles and get the data for the applicability of the differential confocal response curve to see if there is a single zero-crossing point or a good linearity near the zero-crossing point. The goodness-of-fit (GOF) is used to evaluate the accuracy of linear fitting, and can be used as a simple measure method of linearity. And the closer the GOF value is to 1, the higher fitting accuracy is. Through simulation analysis, we can have a better understanding of the advances of divided-aperture differential confocal Raman microscopy.

An improved pseudotargeted GC-MS/MS-based metabolomics method and its application in radiation-induced hepatic injury in a rat model.

The liver is the pivotal metabolic organ primarily responsible for metabolic activities, detoxification and regulation of carbohydrate, protein, amino acid, and lipid metabolism. However, very little is known about the complicated pathophysiologic mechanisms of liver injury result from ionizing radiation exposure. Therefore, a pseudotargeted metabolomics approach based on gas chromatography-tandem mass spectrometry with selected reaction monitoring (GC-MS-SRM) was developed to study metabolic alterations of liver tissues in radiation-induced hepatic injury. The pseudotargeted GC-MS-SRM method was validated with satisfactory analytical characteristics in terms of precision, linearity, sensitivity and recovery. Compared to the SIM-based approach, the SRM scanning method had mildly better precision, higher sensitivity, and wider linear ranges. A total of 37 differential metabolites associated with radiation-induced hepatic injury were identified using the GC-MS-SRM metabolomics method. Global metabolic clustering analysis showed that amino acids, carbohydrates, unsaturated fatty acids, organic acids, metabolites associated with pyrimidine metabolism, ubiquinone biosynthesis and oxidative phosphorylation appeared significantly declined after high dose irradiation exposure, whereas metabolites related to lysine catabolism, glycerolipid metabolism and glutathione metabolism presented the opposite behavior. These changes indicate energy deficiency, antioxidant defense damage, accumulation of ammonia and lipid oxidation of liver tissues in response to radiation exposure. It is shown that the developed pseudotargeted method based on GC-MS-SRM is a useful tool for metabolomics study.

Filter-based ultralow-frequency Raman measurement down to 2 cm-1 for fast Brillouin spectroscopy measurement.

Simultaneous Stokes and anti-Stokes ultralow-frequency (ULF) Raman measurement down to ∼2 cm-1 or 60 GHz is realized by a single-stage spectrometer in combination with volume-Bragg-grating-based notch filters. This system reveals its excellent performance by probing Brillouin signal of acoustic phonons in silicon, germanium, gallium arsenide, and gallium nitride. The deduced sound velocity and elastic constants are in good accordance with previous results determined by various methods. This system can shorten the integration time of the Brillouin signal with a good signal-to-noise ratio by more than 2000-fold compared to a Fabry-Perot interferometer (FPI). This study shows how a filter-based ULF Raman system can be used to reliably achieve Brillouin spectroscopy for condensed materials with high sensitivity and high signal-to-noise ratio, stimulating fast Brillouin spectrum measurements to probe acoustic phonons in semiconductors.