APPLICATION OF DOPPLER OPTICAL COHERENCE TOMOGRAPHY IN RHEOLOGICAL STUDIES:BLOOD FLOW AND VESSELS MECHANICAL PROPERTIES EVALUATION

Doppler Optical Coherence Tomography(DOCT)is a noninvasive optical diagnostic technique,which is well suited for the quantitative mapping of microflow velocity profiles and the analysis of flow-vessel interactions.The noninvasive imaging and quantitative analysis of blood flow in the complex-structured vascular bed is required in many biomedical applications,including those where the determination of mechanical properties of vessels or the knowledge of the mechanic interactions between the flow and the housing medium plays a key role.The change of microvessel wall elasticity could be a potential indicator of cardiovascular disease at the very early stage,whilst monitoring the blood flow dynamics and associated temporal and spatial variations in vessel’s wall shear stress could help predicting the possible rupture of atherosclerotic plaques.The results of feasibility studies of application of DOCT for the evaluation of mechanical properties of elastic vessel model are presented.The technique has also been applied for imaging of sub-cranial rat blood flow in vivo.

The limit properties of spatial coherence of seismic ground motion

The limit properties of spatial coherence of seismic ground motion are studied based on the differential relation between rotation and translation in elastic theory, the results show that the empirical mathematical model of spatial coherence must satisfy some functional characteristics. It is also indicated that the key problem to estimate rotational power spectrum densities is to obtain precisely the two order derivative of spatial coherence.

NUMERICAL RESEARCH ON THE COHERENT STRUCTURE IN THE VISCOELASTIC SECOND-ORDER MIXING LAYERS

Numerical simulations have been performed in time-developing plane mixing layers of the viscoelastic second-order fluids with pseudo-spectral method. Roll-up, pairing and merging of large eddies were examined at high Reynolds numbers and low Deborah numbers. The effect of viscoelastics on the evolution of the large coherent structure was shown by making a comparison between the second-order and Newtonian fluids at the same Reynolds numbers.

Stochastic Second-Order Two-Scale Method for Predicting the Mechanical Properties of Composite Materials with Random Interpenetrating Phase

In this paper,a stochastic second-order two-scale(SSOTS)method is proposed for predicting the non-deterministic mechanical properties of composites with random interpenetrating phase.Firstly,based on random morphology description functions(RMDF),the randomness of the material properties of the constituents as well as the correlation among these random properties are fully characterized through the topologies of the constituents.Then,by virtue of multiscale asymptotic analysis,the random effective quantities such as stiffness parameters and strength parameters along with their numerical computation formulae are derived by a SSOTS strategy combined with the Monte-Carlo method.Finally,the SSOTS method developed in this paper shows an excellent computational accuracy,and therefore present an important advance towards computationally efficient multiscale modeling frameworks considering microstructure uncertainties.

The Wigner function and phase properties of superposition of two coherent states with the vacuum state

This paper discusses some statistical properties of the superposition of two coherent states with a vacuum state, such as sub-Poissonian photon statistics and negativity of the Wigner function. Phase probability distribution and phase variance are calculated. Special cases of the constructed superposition states are presented. The results show that depending on the vacuum state coefficient γ and the coherent state coefficient a, it can generate a variety of nonclassical states.

Quantum Properties of Two-Mode Squeezed Even and Odd Coherent States

Two new types of quantum states are constructed by applying the operator s（ξ） = exp（ξ＊ ab - ξa＋b＋） on the two-mode even and odd coherent states. The mathematical and quantum statistical properties of such states are investigated. Various nonclassical features of these states, such as squeezing properties, the inter-mode photon bunching, and the violation of Cauchy-Schwarz inequality, are discussed. The Wigner function in these states are studied in detail.

Focusing Properties of Partially Coherent Controllable Dark-Hollow Beams through a Thin Lens

Analytical propagation formulas are derived for partially coherent controllable dark-hollow beams （CDHBs） through a thin lens based on the generalized Huygens-Fresnel integral. The expressions of the position for maximum irradiance on-axis and the relative focal shift are evaluated by the analytical propagation formulas. Our numerical results show that both the relative focal shift and the effective beam width of focused partially coherent CDHBs are mainly determined by the initial transverse coherence width 6g and the Fresnel number Nw, which are also affected by the changes of both the dark-size adjusting parameter p and the order N of CDHBs.

Barut-Girardello and Gilmore-Perelomov coherent states for pseudoharmonic oscillators and their nonclassical properties: Factorization method

In this paper we try to introduce the ladder operators associated with the pseudoharmonic oscillator, after solving the corresponding Schrrdinger equation by using the factorization method. The obtained generalized raising and lowering operators naturally lead us to the Dirac representation space of the system which is much easier to work with, in comparison to the functional Hilbert space. The SU（1, 1） dynamical symmetry group associated with the considered system is exactly established through investigating the fact that the deduced operators satisfy appropriate commutation relations. This result enables us to construct two important and distinct classes of Barut-Girardello and Gilmore-Perelomov coherent states associated with the system. Finally, their identities as the most important task are exactly resolved and some of their nonclassical properties are illustrated, numerically.

Photon statistical properties of photon-added two-mode squeezed coherent states

We investigate photon statistical properties of the multiple-photon-added two-mode squeezed coherent states （PA- TMSCS）. We find that the photon statistical properties are sensitive to the compound phase involved in the TMSCS. Our numerical analyses show that the photon addition can enhance the cross-correlation and anti-bunching effects of the PA- TMSCS. Compared with that of the TMSCS, the photon number distribution of the PA-TMSCS is modulated by a factor that is a monotonically increasing function of the numbers of adding photons to each mode; further, that the photon addition essentially shifts the photon number distribution.

Synthesis of Imidazole Derivatives for Their Second-order Nonlinear Optics

The design and the synthesis of two conjugated donor acceptor imidazole derivatives(1, 2) were carried out for second order nonlinear optics. The thermal properties, the transparency and second order nonlinear optical properties of the molecules were investigated. The experimental results indicate that a good nonlinearity transparency thermal stability trade off is achieved for them.

Second-order Nonlinearities of CdS Nanoparticles Studied by Hyper-Rayleigh Scattering Technique

A series of CdS nanoparticles with different surfaces were prepared by colloidal chemical method and reverse micelle method. Their second-order nonlinear optical (NLO) properties were experimentally studied in solution by newly developed hyper-Rayleigh scattering (HRS) technique. The results show that 'per particle' first-order hyperpolarizability beta values are sensitive To the synthetic method and the surface chemical modification.

Simulation of Far-Field Properties of Coherent Vertical Cavity Surface Emitting Laser Array

Far-field properties dependent on array scale, separation, element width and emitted wavelength are system atically analyzed theoretically and experimentally. An array model based on the finite-difference method is established to simulate the far-field profile of the coherent arrays. Some important conclusions are obtained. To achieve a higher quality beam, it is necessary to decrease separation between elements, or to increase the element width. Higher brightness can be achieved in the array with larger scale. Emitted wavelength also has an influence on the far-field profile. These analyses can be extended to the future design of coherent vertical cavity surface emitting laser arrays.

Tightly focused properties of a partially coherent radially polarized power-exponent-phase vortex beam

A partially coherent beam called a radially polarized multi-Gaussian Schell-model power-exponent-phase vortex beam is introduced. Both the analytical formula of the beam propagating through the high-numerical-aperture objective lens based on the vectorial diffraction theory, and the cross-spectral density matrix of the beam in the focal region are derived. Then,the tight focusing characteristics of the partially coherent radially polarized power-exponent-phase vortex beam are studied numerically, and the intensity distribution, degree of polarization and coherence of the beams in the focusing region with different topological charge, power order, beam index and coherence width are analyzed in detail. The results show that the contour of the spot becomes clearer and smoother with the increase in the beam index, and the focal fields of different structures that include the flattened beam can be obtained by changing the coherence width. In addition, by changing the topological charge and power order, the intensity can gather to a point along the ring. These unique properties will have potential applications in particle capture and manipulation, especially in the manipulation of irregular particles.

Statistical Properties of the nonlinear SU（1,1） Coherent States

Using non-Hermitian realizations of SU(1,1) Lie algebra in terms of an f-oscillator, we generalize the notion of nonlinear coherent states to the single-mode and two-mode nonlinear SU(1,1) coherent states. Taking the nonlinearity function , their statistical properties are studied.

Virtual Biopsy and Physical Characterization of Tissues, Biofilms, Implants and Viscoelastic Liquids Using Vibrational Optical Coherence Tomography

Tissue biopsies and implant analysis during animal testing or clinical studies are a requirement for development of new surgical materials and procedures. In this paper we report the use of vibrational OCT (VOCT) to evaluate the viscoelastic behavior of tissues, polymeric materials, biofilms, and viscoelastic solutions of macromolecules. Our results suggest that VOCT is a useful technique to characterize the behavior of cellular tissues and biofilms, polymeric implant materials and viscoelastic solutions used in medicine. It is demonstrated that the modulus and resonant frequency squared per unit thickness is a feature that can be used to characterize a variety of tissues. Further work is needed to understand the generalized behavior of synthetic polymers and viscoelastic solutions.

Far-zone behaviors of scattering-induced statistical properties of partially polarized spatially and spectrally partially coherent electromagnetic pulsed beam

In this study, we explore the far-zero behaviors of a scattered partially polarized spatially and spectrally partially coherent electromagnetic pulsed beam irradiating on a deterministic medium. The analytical formula for the cross-spectral density matrix elements of this beam in the spherical coordinate system is derived. Within the framework of the first-order Born approximation, the effects of the scattering angle θ, the source parameters (i.e., the pulse duration T0 and the temporal coherence length Tcxx), and the scatterer parameter (i.e., the effective width of the medium σR) on the spectral density, the spectral shift, the spectral degree of polarization, and the degree of spectral coherence of the scattered source in the far-zero field are studied numerically and comparatively. Our work improves the scattering theory of stochastic electromagnetic beams and it may be useful for the applications involving the interaction between incident light waves and scattering media.

Viscoelastic Evaluation of Different Hyaluronic Acid Based Fillers Using Vibrational Optical Coherence Tomography

Hylauronic acid (HA) is used as a viscoelastic in Ophthalmology during cataract surgery based on its high viscosity at rest, its ability to shear thin and dissipate energy during phacoemulsification. However, these properties of HA solutions would make them susceptible to migration when used as dermal filler materials. In this study, we apply a new technique termed vibrational optical coherence tomography (VOCT) to compare the physical properties of different HA solutions and fillers used in facial aesthetics. Results presented in this study suggest that HA solutions and HA dermal fillers have markedly different physical properties. HA solutions are highly viscoelastic with high % viscous losses while fillers tend to have lower viscous energy dissipation properties. Clinical observations suggest that the high loss fillers are injected more superficially in the face where tension and internal and external forces are more likely minimized giving tissue of the hands and lips more volume and allowing more natural movement. In contrast, the lower loss gels that are used to lift tissue, generally have a higher G’, and are injected deeper into the face where injection and internal forces are likely to be higher. It is concluded that HA filler gel design can be optimized by use of VOCT to evaluate the % viscous energy loss both in vitro and in vivo.

Analysis of Mechanical Behavior of Composite Tissues Using Vibrational Optical Coherence Tomography

Extracellular matrices (ECMs) found in vertebrate tissues are fiber reinforced composite materials that prevent premature mechanical failure, store, transmit, and dissipate mechanical energy generated by the musculoskeletal system. We have developed a new method using optical cohesion tomography and vibrational analysis to non-destructively and non-invasively measure the mechanical properties of composite tissues and polymeric materials. In addition, this method can be used to measure the moduli of individual components of composite materials and perform “mechanical spectroscopy” on materials. In addition, we propose that measurement of the resonant frequency of a material minimizes the viscoelastic behavior of a composite material. This approach simplifies the analysis of mechanical behavior of polymers and others materials that demonstrate time-dependence to their properties.

Non-Invasive and Non-Destructive Determination of Corneal and Scleral Biomechanics Using Vibrational Optical Coherence Tomography: Preliminary Observations

Experimental measurements made in this study on human and porcine eyes suggest that the resonant frequency for both cornea and sclera varies from 130 to 150 Hz and increases slightly with increasing intraocular pressure. The values of the moduli calculated using the experimental values of the thickness are close to 2 MPa. Similar values of the modulus for cornea and sclera suggest that there is very little stress concentration at the cornea-scleral junction and that any stress concentration that occurs probably resides at the scleral attachment laterally and posteriorly. These moduli are close to those measured in vivo on human skin suggesting that the mechanism of tensile deformation of skin, cornea and sclera are similar. Our results suggest that the modulus of cornea and sclera can be measured non-invasively and non-destructively using vibrational OCT. Results of these studies will assist clinicians to better understand the influence of biomechanics on the outcome of corneal refractive surgery as well as the pathogenesis of eye disorders such as glaucoma, myopia and keratoconus.

Propagation of the off-axis superposition of partially coherent beams through atmospheric turbulence

The propagation properties of the off-axis superposition of partially coherent beams through atmospheric turbulence and their beam quality in terms of the mean-squared beam width w（z） and the power in the bucket （PIB） are studied in detail, where the effects of partial coherence, off-axis beam superposition and atmospheric turbulence are considered. The analytical expressions for the intensity, the beam width and the PIB are derived, and illustrative examples are given numerically. It is shown that the maximum intensity/max and the PIB decrease and w（z） increases as the refraction index structure constant Cn^2 increases. Therefore, the turbulence results in a degradation of the beam quality. However, the resulting partially coherent beam with a smaller value of spatial correlation parameter γ and larger values of separate distance Xd and beam number M is less affected by the turbulence than that with a larger value of y and smaller values of Xd and M. The main results obtained in this paper are explained physically.