Search

We show that applying the Laplace operator to a speckle-free quantitative phase image reveals an unprecedented level of detail in cell structure, without the gradient artifacts associated with differential interference contrast microscopy, or photobleaching and phototoxicity limitations common in fluorescence microscopy. This method, referred to as Laplace phase microscopy, is an efficient tool for tracking vesicles and organelles in living cells. The principle is demonstrated by tracking organelles in cardiomyocytes and vesicles in neurites of hippocampal neurons, which to our knowledge are the first label-free diffusion measurements of the organelles in such cells.

Recently, Wolf has shown that the phase measurement associated with fields that are not monochromatic, which is relevant for all x-ray structure investigations, must be properly defined via a cross-spectral density function under full spatial coherence conditions; otherwise, the problem is meaningless and has no solution [E. Wolf, Phys. Rev. Lett. 103, 075501 (2009)]. We propose an experimental realization for retrieving the phase across the entire field of an image. The demonstration is performed using broadband optical fields, but can be extended to other electromagnetic radiation, including x-rays.

We present Instantaneous Spatial Light Interference Microscopy (iSLIM) as a new quantitative phase method that combines the benefits of white light illumination in Zernike’s phase contrast microscopy and phase stability associated diffraction phase microscopy. iSLIM is implemented as an add-on module to a commercial phase contrast microscope, and enables new features to quantitative phase imaging: diminished speckle effects due to white light illumination, multimodal investigation potential due to overlaying with other modalities of the microscope (e.g. fluorescence, DIC, phase contrast), and spectroscopic potential due to the broad band light. We show proof of principle results by multicolor phase imaging of microsphere and red blood cells, and dynamic imaging of nanoscale cell membrane fluctuations.

We present the light scattering of individual Plasmodium falciparum-parasitized human red blood cells Pf-RBCs, and demonstrate progressive alterations to the scattering signal arising from the development of malaria-inducing parasites. By selectively imaging the electric fields using quantitative phase microscopy and a Fourier transform light scattering technique, we calculate the light scattering maps of individual Pf-RBCs. We show that the onset and progression of pathological states of the Pf-RBCs can be clearly identified by the static scattering maps. Progressive changes to the biophysical properties of the Pf-RBC membrane are captured from dynamic light scattering. © 2010 Society of Photo-Optical Instrumentation Engineers.

Blood smear analysis has remained a crucial diagnostic tool for pathologists despite the advent of automatic analyzers such as flow cytometers and impedance counters. Though these current methods have proven to be indispensible tools for physicians and researchers alike, they provide limited information on the detailed morphology of individual cells, and merely alert the operator to manually examine a blood smear by raising flags when abnormalities are detected. We demonstrate an automatic interferometry-based smear analysis technique known as diffraction phase cytometry (DPC), which is capable of providing the same information on red blood cells as is provided by current clinical analyzers, while rendering additional, currently unavailable parameters on the 2-D and 3-D morphology of individual red blood cells. To validate the utility of our technique in a clinical setting, we present a comparison between tests generated from 32 patients by a state of the art clinical impedance counter and DPC.

We demonstrate Diffraction Phase Cytometry (DPC) as a single shot, full-field, high throughput quantitative phase imaging modality, dedicated to analyzing whole blood smears. Utilizing a commercial CD as a sample substrate, along with dynamic spatial filtering via a liquid crystal spatial light modulator, we have developed a compact instrument capable of making quantitative, physiologically relevant measurements. To illustrate the ability of the system to function as a highly sensitive cytometer we imaged a large number (N=1,537) of live human erythrocytes in whole blood without preparation. We retrieved a comprehensive set of geometrical parameters including cell volume and surface area, which are not directly available using existing cytometers. Furthermore, we retrieved the minimum cylindrical diameter, through which red blood cells can pass, and deliver oxygen. These initial results prove the concept for an inexpensive lab-on-a-chip blood screening device.

The European Union proposed a new model of economy, at this beginningof century and millennium: the economy of knowledge, simultaneous with the emergenceof a new existential reality for us people, after Christ was born; this new, existentialreality are the climatic changes.In spite of the warning signals drawn by specialists, the more profound conquests ofscience, only a new educational model can save the humankind of a galloping fall inpromiscuity but also in eternity.

We present a technique for 3D imaging of live cells in translational motion without need of axial scanning of objective lens. A set of transmitted electric field images of cells at successive points of transverse translation is taken with a focused beam illumination. Based on Hyugens' principle, angular plane waves are synthesized from E-field images of a focused beam. For a set of synthesized angular plane waves, we apply a filtered back-projection algorithm and obtain 3D maps of refractive index of live cells. This technique, which we refer to as synthetic aperture tomographic phase microscopy, can potentially be combined with flow cytometry or microfluidic devices, and will enable high throughput acquisition of quantitative refractive index data from large numbers of cells.

We developed an interferometric microscopy technique, referred to as Jones phase microscopy, capable of extracting the spatially resolved Jones polarization matrix associated with transparent and anisotropic samples. This is a generalization of quantitative phase imaging, which is recovered from one diagonal element of the measured matrix. The principle of the technique is demonstrated with measurements of a liquid crystal spatial light modulator and the potential for live cell imaging with experiments on live neurons in culture.

We employ a novel optical technique, dynamic scattering microscopy (DSM), to extract the frequency dependence of the viscoelastic modulus associated with the red blood cell membrane. This approach applies the principle of dynamic light scattering to micro beads attached to the red blood cell membrane in thermal fluctuation. This allows for highthroughput characterization of a large number of cells simultaneously, which represents a significant advantage over current methods. The results in terms of the effective loss and storage moduli indicate the generic behavior of a viscoelastic material, characterized by power laws with exponents between 0 and 1.

This PDF file contains the errata for “JBO Vol. 11 Issue 05 Paper 2362857” for JBO Vol. 11 Issue 05

We quantify the nanoscale structure and low-frequency dynamics associated with live red blood cells. The membrane displacements are measured using quantitative phase images provided by Fourier phase microscopy, with an average path-length stability of 0.75 nm over 45 min. The results reveal the existence of dynamic, independent subdomains across the cells that fluctuate at various dominant frequencies.

We introduce Hilbert phase microscopy (HPM) as a novel optical technique for measuring high transverse resolution quantitative phase images associated with optically transparent objects. Because of its single-shot nature, HPM is suitable for investigating rapid phenomena that take place in transparent structures such as biological cells. The potential of this technique for studying biological systems is demonstrated with measurements of red blood cells, and its ability to quantify dynamic processes on a millisecond scale is exemplified with measurements of evaporating micrometer-sized water droplets.

Harmonic phase-dispersion microscopy (PDM) is a new imaging technique in which contrast is provided by differences in refractive index at two harmonically related wavelengths. We report a new configuration of the harmonic phase-dispersion microscope in a Mach-Zehnder geometry as an instrument for imaging biological samples. Several improvements on the earlier design are demonstrated, including a single-pass configuration and acousto-optic modulators for generating the heterodyne signals without mechanical arm scanning. We demonstrate quantitative phase-dispersion images of test structures and biological samples.

We present a new quantitative method for investigating red blood cell morphology and dynamics. The instrument integrates quantitative phase microscopy with an inverted microscope, which makes it particularly suitable for the noninvasive assessment of live erythrocytes. In particular, we demonstrate the ability of this approach to quantify noninvasively cell volume and dynamic morphology. The subnanometer path-length sensitivity at the millisecond time scales is exemplified by measuring the hemoglobin flow out of the cell during hemolysis.

By use of the Fourier decomposition of a low-coherence optical image field into two spatial components that can be controllably shifted in phase with respect to each other, a new high-transverse-resolution quantitative-phase microscope has been developed. The technique transforms a typical optical microscope into a quantitative-phase microscope, with high accuracy and a path-length sensitivity of lambda/5500, which is stable over several hours. The results obtained on epithelial and red blood cells demonstrate the potential of this instrument for quantitative investigation of the structure and dynamics associated with biological systems without sample preparation.

For describing the fluctuating signal scattered from a multiple-scattering system, diffusive-wave spectroscopy makes use of a diffusion model that provides the path-length distribution of scattered waves for a specific geometry. Using the recently introduced optical path-length spectroscopy, we show that the diffusion model fails to describe wave propagation in the low-order multiple-scattering regime. We propose a new methodology with which to obtain information about the dynamic properties of nondiffusive scattering systems. We use optical path-length spectroscopy to obtain experimentally the path-length distribution of optical waves scattered from dynamic colloids, which are multiply scattering but not in the diffusion limit. The experimental results show that, with this new technique, the accuracy of dynamic measurements is significantly improved in subdiffusive scattering regimes.

We propose optical path-length spectroscopy as a new approach to obtaining information from media that exhibit multiple light scattering. By using a backscattering technique based on low-coherence interferometry, we are able to determine the optical path-length distribution for light reflected from a random medium and to infer the value of the transport mean free path. We illustrate how a diffusion approximation model leads to a satisfactory description of depth-resolved profiles of the backscattered intensity and discuss potential applications of this technique.

This study aims at conceiving a strategic training and reference assessment system concerning the balance component, according to the diverse Special Olympics gymnasts’ potential. The experimental group includes 24 beginner gymnasts, within level A and level I. Due to our practical experience and statistical confirmations, we believe that the mentioned evaluation system should comprise three general tests (Romberg Matorin, Unipodal test,), a specific test (the level A beam routine) and three reference technical tests (three side rolls towards left and three towards right with a stand lifting, maintained sat set square - execution, held side balance time-trial). Also, a specific adapted instructional content has been developed, so that this motor capacity should improve in a significant manner.

Due to specific conditions, inclusive education in Romania is one of the priorities in terms of know-how, instruction, education and also, changing mentalities. The aim of this study is to identify whether the unified sports and gymnastics in particular have positive effects upon motor components and behavioural aspects in mentally disabled children .The methods we used in this research were the pedagogical observation and the experiment with transverse approaches. The experimental group includes 100 competitors (50 with intellectual disabilities and 50 children from mainstream schools), both girls and boys, aged between 8 and 32.In order to assess the quantitative and quality effects, individual times and deduction times were taken for each applicative path that children performed. Each element from the route has certain specific demands, so that the deficient areas observed during its performing will be improved by consistent training. By means of the oriented observation, strong points, as well as weaknesses were identified, in terms of motor, psychomotor and social abilities. Comparative results of the abled and disabled subjects, statistically processed, confirm the complex influences of gymnastics means on educational, motor and behavioural levels. Unified gymnastics competitions reveal a new dynamic approach in fulfilling the objectives of the inclusive physical education. Such an applicative path, with gymnastics elements could further become a complex test for motor, psychomotor abilities, capacities, required and enhanced in physical education classes.

We present white-light diffraction phase microscopy (wDPM) as a fast and sensitive quantitative phase imaging method and a successive derivatives based phase reconstruction method. We illustrate the utility of wDPM with measurements on live cells.

We used quantitative phase imaging to measure the dispersion relation, i.e. decay rate vs. spatial mode, associated with mass transport in live cells. This approach applies equally well to both discrete and continuous mass distributions without the need for particle tracking. From the quadratic experimental curve specific to diffusion, we extracted the diffusion coefficient as the only fitting parameter. The linear portion of the dispersion relation reveals the deterministic component of the intracellular transport. Our data show a universal behavior where the intracellular transport is diffusive at small scales and deterministic at large scales. Measurements by our method and particle tracking show that, on average, the mass transport in the nucleus is slower than in the cytoplasm.

We present a reflection-based broadband illumination quantitative phase imaging technique that provides halo-free images of opaque samples with sub-nanometer spatial and temporal noise.

Spatial light interference microscopy (SLIM) is a novel method developed in our laboratory that provides quantitative phase images of transparent structures with a 0.3 nm spatial and 0.03 nm temporal accuracy owing to the white light illumination and its common path interferometric geometry. We exploit these features and demonstrate SLIM's ability to perform topography at a single atomic layer in graphene. Further, using a decoupling procedure that we developed for cylindrical structures, we extract the axially averaged refractive index of semiconductor nanotubes and a neurite of a live hippocampal neuron in culture. We believe that this study will set the basis for novel high-throughput topography and refractometry of man-made and biological nanostructures.

We developed a theoretical and experimental approach that allows for solving the 3D scattering inverse problem via quantitative phase imaging with broadband fields.

This paper describes a model for the prediction of micro-plastic material transformation and associated residual stress field development in bearing steels during over-rolling. The high and mainly hydrostatic pressure field induced by the rolling element load, leads to the development of micro-plastic deformation in the subsurface layer of the rolling contact. The resulting plastic strain distribution gives rise to an associated self-equilibrating residual stress field that can be experimentally quantified using X-ray diffraction methods. A novel three-dimensional elastic-plastic over-rolling solution is used to evaluate the plastic strains and material transformation. Central to this plastic contact formulation is the incremental approach to deal with nonlinear material behavior. The Prandtl-Reuss constitutive equations in conjunction with Huber-Mises-Hencky yield criterion and Ramberg-Osgood strain-hardening relationships are applied to describe the plastic behavior of common hardened bearing steels. A nonlinear isotropic law is applied to describe the transformation of the retained austenite during stress cycles and changes in the strain-hardening behavior of the material microstructure. Application of this model with an incremental solution scheme based on the Conjugate Gradient Method (CGM) gives good convergence properties and fast solution for each cycle. Comparison between experimentally obtained residual stresses and stress fields derived from the present micro-plastic contact model, indicates good agreement. Numerical simulations, carried out to derive the maximum operating contact pressures in the elastic regime are also in agreement with published data. The model opens new possibilities in the evaluation of steels and heat treatments used in rolling bearings. Furthermore, this micro-plastic contact model may help the interpretation of the load history leading to a given pattern of residual stress measured in bearing rings.