Optical single-pixel volumetric imaging by three-dimensional light-field illumination.

Three-dimensional single-pixel imaging (3D SPI) has become an attractive imaging modality for both biomedical research and optical sensing. 3D-SPI techniques generally depend on time-of-flight or stereovision principle to extract depth information from backscattered light. However, existing implementations for these two optical schemes are limited to surface mapping of 3D objects at depth resolutions, at best, at the millimeter level. Here, we report 3D light-field illumination single-pixel microscopy (3D-LFI-SPM) that enables volumetric imaging of microscopic objects with a near-diffraction-limit 3D optical resolution. Aimed at 3D space reconstruction, 3D-LFI-SPM optically samples the 3D Fourier spectrum by combining 3D structured light-field illumination with single-element intensity detection. We build a 3D-LFI-SPM prototype that provides an imaging volume of ∼390 × 390 × 3,800 µm3 and achieves 2.7-µm lateral resolution and better than 37-µm axial resolution. Its capability of 3D visualization of label-free optical absorption contrast is demonstrated by imaging single algal cells in vivo. Our approach opens broad perspectives for 3D SPI with potential applications in various fields, such as biomedical functional imaging.

Canibacter zhuwentaonis sp. nov. and Canibacter zhoujuaniae sp. nov., isolated from Marmota himalayana.

Four Gram-stain-positive, facultatively anaerobic, non-motile, non-spore-forming and rod-shaped bacteria (lx-72T, lx-45, ZJ784T and ZJ955) were isolated from the respiratory tract or faeces of marmot (Marmota himalayana) from the Qinghai-Tibet Plateau in China. Analysis of the 16S rRNA gene sequences showed that all strains belong to the genus Canibacter and are more related to Canibacter oris CCUG 64069T (95.1-97.4 % similarity) than to the genus Leucobacter. Both strain pairs grew well at pH 6-9 and 15-42°C, and ZJ784T/ZJ955 could tolerate slightly higher NaCl (0.5-4.5 %, w/v) than lx-72T/lx-45(0.5-3.5 %). Based on whole-genome sequences, the average nucleotide identity and digital DNA-DNA hybridization values between our four isolates and their closest relative were below the species delineation thresholds of 70 % and 95-96 %. The common major fatty acids (>10 %) of our four strains were anteiso-C15 : 0 and anteiso-C17 : 0. For both new type strains, MK-8(H4) and MK-9(H4) were the major isoprenoid quinones, and diphosphatidylglycerol and phosphatidylglycerol were the main polar lipids. The genomic DNA G+C content of all strains was 53.9 mol%. Based on results from the genomic comparison, phylogenetic analysis, and physiological and biochemical characteristics, the four isolates represent two novel species in the genus Canibacter, for which the names Canibacter zhuwentaonis sp. nov. (type strain lx-72T=KCTC 49658T=GDMCC 1.2569T) and Canibacter zhoujuaniae sp. nov. (type strain ZJ784T=KCTC 49507T=GDMCC 1.1997T) are proposed.

Optical tweezers study of membrane fluidity in small cell lung cancer cells.

The fluidity of the cell membrane is closely related to cancer metastasis/invasion. To test the relationship of membrane fluidity and invasiveness, we first demonstrated that transfection of small RNA miR-92b-3p can significantly increase invasiveness of the small cell lung cancer cell line SHP77. Then optical tweezers were used to measure membrane fluidity. This study employed continuous and step-like stretching methods to examine fluidity changes in SHP77 cell membranes before and after miR-92b-3p transfection. A newly developed physical model was used to derive the effective viscosity and static tension of the cell membrane from relaxation curves obtained via step-like stretching. Experiments showed that invasiveness and fluidity increased significantly after miR-92b-3p transfection. This study paved the way toward a better understanding of cancer cell invasion and membrane mechanical characteristics.

Single-pixel spiral phase contrast imaging.

In this Letter, we present single-pixel spiral phase contrast imaging that enables optical edge detection of both amplitude and phase objects. This technique utilizes single-pixel detection to directly acquire the Fourier spectrum of the edge-enhanced object by scanning spiral phase-encoded plane waves in k-space. Experimentally, we exploit a digital micromirror device to simultaneously generate the plane wave and reference field for illuminating the object and scan the plane wave for spectrum sampling. During the process, four-step phase-shifting is adopted, and synchronized intensity measurements are made with a single-pixel detector. Applying an inverse Fourier transform to the obtained spectrum directly yields the edge information of objects. As a demonstration, digital and real objects are imaged, and results verify that isotropic edge detection can be achieved with our technique for both amplitude and phase objects.

Dynamic shaping of orbital-angular-momentum beams for information encoding.

Shaping complex fields with a digital micromirror device (DMD) has attracted much attention recently due to its potential application in optical communication and microscopy. In this paper, we present an optimized Lee method to achieve dynamic shaping of orbital-angular-momentum (OAM) beams using a binary DMD. An error diffusion algorithm is introduced to enhance the accuracy for binary-amplitude hologram design, making it possible to achieve high fidelity wavefront shaping while retaining a high resolution. As a proof of concept, we apply this method to create different classes of OAM beams. The numerical simulations verify that a fidelity of F > 0.985 can be achieved for all the test OAM fields with fully independent phase and amplitude modulation. Moreover, we experimentally demonstrate the dynamic shaping of different OAM beams including pure modes and mixed modes with a switching rate of up to 17.8 kHz. On this basis, accurate information encoding into the generated multiplexed OAM beams is accomplished, which provides access to high speed classical and quantum communications that employ spatial mode encoding.

Orbit-induced localized spin angular momentum in the tight focusing of linearly polarized vortex beams.

Optical spin-orbit interaction has gained much interest recently due to its universality and importance in modern photonics. In this Letter, we theoretically demonstrate that orbit-induced localized spin angular momentum (SAM) conversion can occur in the tight focusing of spin-free linearly polarized vortex beams (LPVBs). By analysis of the polarization states that are associated with the SAM density, we attribute the occurrence of such a conversion to the helical-phase-induced change of local polarization states in the focused field. In the local SAM, density can be further regulated by altering the sign and value of the orbital angular momentum in the incident LPVBs, as well as their polarization orientations. This Letter is expected to advance our understanding of optical spin-orbit coupling and benefit applications of optical microscopy and trapping.

Association of newborn screening metabolites with risk of wheezing in childhood.

BACKGROUND: There are critical gaps in our understanding of the temporal relationships between metabolites and subsequent asthma development. This is the first study to examine metabolites from newborn screening in the etiology of early childhood wheezing. METHODS: One thousand nine hundred and fifty one infants enrolled between 2012 and 2014 from pediatric practices located in Middle Tennessee in the population-based birth cohort study, the Infant Susceptibility to Pulmonary Infections and Asthma Following RSV Exposure Study (INSPIRE), were linked with metabolite data from the Tennessee Newborn Screening Program. The association between the levels of 37 metabolites and the number of wheezing episodes in the past 12 months was assessed at 1, 2, and 3 years of life. RESULTS: Several metabolites were significantly associated with the number of wheezing episodes. Two acylcarnitines, C10:1 and C18:2, showed robust associations. Increasing levels of C10:1 were associated with increasing number of wheezing episodes at 2 years (OR 2.11, 95% CI 1.41-3.17) and 3 years (OR 2.56, 95% CI 1.59-4.11), while increasing levels of C18:2 were associated with increasing number of wheezing episodes at 1 year (OR 1.38, 95% CI 1.12-1.71) and 2 years (OR 1.47, 95% CI 1.17-1.84). CONCLUSIONS: Identification of specific metabolites and associated pathways involved in wheezing pathogenesis offer insights into potential targets to prevent childhood asthma morbidity.

Oscillations of absorbing particles at the water-air interface induced by laser tweezers.

We present an experimental study on oscillation of absorbing particles at the water-air interface. The oscillation is induced by laser tweezers, which are generated with a high numerical aperture objective. When the laser beam is tightly focused at the water-air interface, the optical gradient force attracts the particles to the spot center, and the laser heating of particles results in a strong thermal gradient that drives the particles to leave the spot center. Under the action of thermal and optical gradient force together, the absorbing particles oscillate at the water-air interface.

Aberration compensation for optical trapping of cells within living mice.

Optical tweezers have been used to trap and manipulate microparticles within living animals. When the optical trap is constructed with an oil-immersion objective, it suffers from spherical aberration. There have been many investigations on the influence of spherical aberration when the particles are trapped in a water medium. However, the dependence of optical force on trapping depth is still ambiguous when the trapped particles are immersed in a high refractive index medium (such as biological tissue, refractive index solution) in experiments. In this paper, the microparticles are immersed in an aqueous solution of glycerol to mimic the cells within biological tissue. As the trapping laser is focused into the specimen, spherical aberration is introduced, degrading the optical trapping performance. It is similar to trapping in water; altering the effective tube length can also compensate for the spherical aberration of the optical trap in a high refractive index medium. Finally, the cells in living mice are trapped by the optical tweezers with the help of spherical aberration compensation.

Calibrating oscillation response of a piezo-stage using optical tweezers.

In optical tweezers, a piezo-stage (PZT) is widely used to precisely position samples for force clamp, calibrating optical trap and stretching DNA. For a trapped bead in solution, the oscillation response of PZT is vital for all kinds of applications. A coupling ratio, actual amplitude to nominal amplitude, can be calibrated by power spectral density during sinusoidal oscillations. With oscillation frequency increasing, coupling ratio decreases in both x- and y-directions, which is also confirmed by the calibration with light scattering of scanning two aligned beads on slide. Those oscillation responses are related with deformability of chamber and the intrinsic characteristics of PZT. If we take nominal amplitude as actual amplitude for sinusoidal oscillations at 50 Hz, the amplitude is overestimated ~2 times in x-direction and ~3 times in y-direction. That will lead to huge errors for subsequent calibrations.

Shaping diffraction-free Lommel beams with digital binary amplitude masks.

Here, we report on experimental observations of various Lommel modes that possess distinct diffraction-free behaviors. The binary amplitude masks are designed to accurately encode the complex field information with the superpixel method. Then, the generation of the desired beams is demonstrated with these binary patterns projected onto the digital micromirrors device (DMD). Remarkably, we find that the field distribution and orbital angular momentum can be continuously engineered by tuning the beam parameters. Furthermore, the shape-invariant feature of such beams is verified by their far-field ring-like structures. Our observations are in good accordance with the theoretical predictions, and our methods may find potential applications in optical guiding and imaging. Moreover, apart from the DMD, the binary amplitude hologram can also be presented with well-fabricated elements, and thus, our method will also enable new applications for surface plasmon polaritons as well as electron beams.

Calibration of optical tweezers based on an autoregressive model.

The power spectrum density (PSD) has long been explored for calibrating optical tweezers stiffness. Fast Fourier Transform (FFT) based spectral estimator is typically used. This approach requires a relatively longer data acquisition time to achieve adequate spectral resolution. In this paper, an autoregressive (AR) model is proposed to obtain the Spectrum Density using a limited number of samples. According to our method, the arithmetic model has been established with burg arithmetic, and the final prediction error criterion has been used to select the most appropriate order of the AR model, the power spectrum density has been estimated based the AR model. Then, the optical tweezers stiffness has been determined with the simple calculation from the power spectrum. Since only a small number of samples are used, the data acquisition time is significantly reduced and real-time stiffness calibration becomes feasible. To test this calibration method, we study the variation of the trap stiffness as a function of the parameters of the data length and the trapping depth. Both of the simulation and experiment results have showed that the presented method returns precise results and outperforms the conventional FFT method when using a limited number of samples.

Observation of the asymmetric Bessel beams with arbitrary orientation using a digital micromirror device.

Recently, V. V. Kotlyar et al. [Opt. Lett.39, 2395 (2014)] have theoretically proposed a novel kind of three-parameter diffraction-free beam with a crescent profile, namely, the asymmetric Bessel (aB) beam. The asymmetry degree of such nonparaxial modes was shown to depend on a nonnegative real parameter c. We present a more generalized asymmetric Bessel mode in which the parameter c is a complex constant. This parameter controls not only the asymmetry degree of the mode but also the orientation of the optical crescent, and affects the energy distribution and orbital angular momentum (OAM) of the beam. As a proof of concept, the high-quality generation of asymmetric Bessel-Gauss beams was demonstrated with the super-pixel method using a digital micromirror device (DMD). We investigated the near-field properties as well as the far field features of such beams, and the experimental observations were in good agreement with the theoretical predictions. Additionally, we provided an effective way to control the beam's asymmetry and orientation, which may find potential applications in light-sheet microscopy and optical manipulation.

Risk assessment for the long-term stability of fly ash-based cementitious material containing arsenic: Dynamic and semidynamic leaching.

Fly ash from municipal solid waste incineration (MSWIFA) contains leachable heavy metals (HMs), and the environmental risk of contained HMs is an important concern for its safe treatment and disposal. This paper presents a dynamic leaching test of fly ash-based cementitious materials containing arsenic (FCAC) in three particle sizes based on an innovative simulation of two acid rainfall conditions to investigate the long-term stability of FCAC under acid rain conditions. As well as semi-dynamic leaching test by simulating FCAC in three scenarios. Furthermore, the long-term stability risk of FCAC is evaluated using a sequential extraction procedure (SEP) and the potential risk assessment index. Results showed that the Al3+ in the FCAC dissolved and reacted with the OH- in solution to form Al(OH)3 colloids as the leaching time increased. Moreover, the oxidation of sulfide minerals in the slag produced oxidants, such as H2SO4 and Fe2(SO4)3, which further aggravated the oxidative dissolution of sulfides, thereby resulting in an overall decreasing pH value of the leachate. In addition, due to the varying particle sizes of the FCAC, surface area size, and adsorption site changes, the arsenic leaching process showed three stages of leaching characteristics, namely, initial, rapid, and slow release, with a maximum leaching concentration of 2.42 mg/L, the cumulative release of 133.78 mg/kg, and the cumulative release rate of 2.32%. The SEP test revealed that the reduced state of HMs in the raw slag was lowered substantially, and the acid extractable state and residual state of HMs were increased, which was conducive to lessening the risk of FCAC. Overall, the geological polymerization reaction of MSWIFA is a viable and promising solution to stabilize mining and industrial wastes and repurpose the wastes into construction materials.

Optical trapping of red blood cells in living animals with a water immersion objective.

We demonstrate optical trapping of red blood cells (RBCs) in living animals by using a water immersion objective. First, the cells within biological tissue are mimicked by the particles immersed in aqueous solutions of glycerol. The optical forces depending on trapping depth are investigated when a parallel laser beam enters the water immersion objective. The results show that the optical forces vary with trapping depth, and the optimal trapping depth in aqueous solutions of glycerol (n=1.39) is 50 µm. Second, the optimal trapping depth in aqueous solutions of glycerol can be changed by altering the actual tube length of the water immersion objective. Finally, we achieved optical trapping and manipulation of RBCs in living mice.

Generation of nondiffracting Bessel beam using digital micromirror device.

We experimentally demonstrated Bessel-like beams utilizing digital micromirror device (DMD). DMD with images imitating the equivalent axicon can shape the collimated Gaussian beam into Bessel beam. We reconstructed the 3D spatial field of the generated beam through a stack of measured cross-sectional images. The output beams have the profile of Bessel function after intensity modulation, and the beams extend at least 50 mm while the lateral dimension of the spot remains nearly invariant. Furthermore, the self-healing property has also been investigated, and all the experimental results agree well with simulated results numerically calculated through beam propagation method. Our observations demonstrate that the DMD offers a simple and efficient method to generate Bessel beams with distinct nondiffracting and self-reconstruction behaviors. The generated Bessel beams will potentially expand the applications to the optical manipulation and high-resolution fluorescence imaging owing to the unique nondiffracting property.

Associations between Smoking and Smoking Cessation during Pregnancy and Newborn Metabolite Concentrations: Findings from PRAMS and INSPIRE Birth Cohorts.

Newborn metabolite perturbations may identify potential biomarkers or mechanisms underlying adverse, smoking-related childhood health outcomes. We assessed associations between third-trimester smoking and newborn metabolite concentrations using the Tennessee Pregnancy Risk Assessment Monitoring System (PRAMS, 2009-2019) as the discovery cohort and INSPIRE (2012-2014) as the replication cohort. Children were linked to newborn screening metabolic data (33 metabolites). Third-trimester smoking was ascertained from birth certificates (PRAMS) and questionnaires (INSPIRE). Among 8600 and 1918 mother-child dyads in PRAMS and INSPIRE cohorts, 14% and 13% of women reported third-trimester smoking, respectively. Third-trimester smoking was associated with higher median concentrations of free carnitine (C0), glycine (GLY), and leucine (LEU) at birth (PRAMS: C0: adjusted fold change 1.11 [95% confidence interval (CI) 1.08, 1.14], GLY: 1.03 [95% CI 1.01, 1.04], LEU: 1.04 [95% CI 1.03, 1.06]; INSPIRE: C0: 1.08 [95% CI 1.02, 1.14], GLY: 1.05 [95% CI 1.01, 1.09], LEU: 1.05 [95% CI 1.01, 1.09]). Smoking cessation (vs. continued smoking) during pregnancy was associated with lower median metabolite concentrations, approaching levels observed in infants of non-smoking women. Findings suggest potential pathways underlying fetal metabolic programming due to in utero smoke exposure and a potential reversible relationship of cessation.

Calculation of optical forces on an ellipsoid using vectorial ray tracing method.

For a triaxial ellipsoid in an optical trap with spherical aberration, the optical forces, torque and stress are analyzed using vectorial ray tracing. The torque will automatically regulate ellipsoid's long axis parallel to optic axis. For a trapped ellipsoid with principal axes in the ratio 1:2:3, the high stress distribution appears in x-z plane. And the optical force at x-axis is weaker than at y-axis due to the shape size. While the ellipsoid departs laterally from trap center, the measurable maximum transverse forces will be weakened due to axial equilibrium and affected by inclined orientation. For an appropriate ring beam, the maximum optical forces are strong in three dimensions, thus, this optical trap is appropriate to trap cells for avoiding damage from laser.

Developing an Online Dashboard to Visualize Performance Data-Tennessee Newborn Screening Experience.

Newborn screening (NBS) is a vital public health program and delays in the screening process can lead to catastrophic outcomes for infants and their families. Efforts to improve screening quality in Tennessee are proactive and ongoing. From these efforts, an open-access dashboard has been developed to address a need for methods to better visualize performance data, promote data transparency, and drive quality improvement. Dashboard development was a collaboration between a fellow from the Association of Public Health Laboratories (APHL) and Tennessee NBS staff. Iterative dashboard prototypes were developed using Tableau software and incorporated feedback from Tennessee birthing facility staff and health experts. Infrastructure and procedures were created to reduce the burden of future dashboards. Eight NBS performance indicators are visualized across several views. These views are designed to provide an overview of NBS performance data when first accessed, then allow for a drill-down into specific data. This dashboard drives introspection at the state and facility level, making it possible to identify potential issues and necessary corrective actions earlier, therefore improving the completeness and timeliness of NBS in Tennessee. The experiences from developing this dashboard can be applied to future dashboard development in Tennessee NBS and other public health programs implementing similar measures.

Experimental generation of Laguerre-Gaussian beam using digital micromirror device.

A digital micromirror device (DMD) modulates laser intensity through computer control of the device. We experimentally investigate the performance of the modulation property of a DMD and optimize the modulation procedure through image correction. Furthermore, Laguerre-Gaussian (LG) beams with different topological charges are generated by projecting a series of forklike gratings onto the DMD. We measure the field distribution with and without correction, the energy of LG beams with different topological charges, and the polarization property in sequence. Experimental results demonstrate that it is possible to generate LG beams with a DMD that allows the use of a high-intensity laser with proper correction to the input images, and that the polarization state of the LG beam differs from that of the input beam.