Non-interferometric transient quantitative phase microscopy for ultrafast engineering

Lead-free piezoelectric ceramics Bi_0.5(Na_1-x-yK_xAg_y)_0.5TiO₃ [BNKAT(x/y)] have been synthesized by the mixed oxide method. The effects of the amount of K⁺ and Ag⁺ on the electrical properties were examined. X-ray diffraction patterns indicate that K⁺ and Ag⁺ ions partially substitute for the Na⁺ ions in Bi_0.5Na_0.5TiO₃ and form a solid solution during sintering. At room temperature, the ceramics exhibit good performances with piezoelectric constant d₃₃=189 pC/N, electromechanical coupling factor k_p=35.0%, remanent polarization P_r=39.5 μC/cm², and coercive field E_c=3.3 kV/mm, respectively. The curves of the dielectric constant ε_r and loss tangent tan δ versus temperature show that the transition temperature from ferroelectric to anti-ferroelectric phase decreases with increasing the K⁺ content for the compositions researched. The dependencies of k_p and polarization versus electric (P–E) hysteresis loops on temperature reveal that the depolarization temperature T_d of BNKAT(0.15/0.015) ceramics, which have good piezoelectric properties (d₃₃=134 pC/N, k_p=32.5%) and strong ferroelectricity (P_r=39.5 μC/cm², E_c=4.1 kV/mm) at room temperature, is above 160 °C. PACS 77.22.-d; 77.65.Bn; 77.80.Bh; 77.80.Dj; 77.84.Dy     

Broadly tunable single-frequency cw mid-infrared source with milliwatt-level output based on difference-frequency generation in orientation-patterned GaAs

A narrow-linewidth mid-IR source based on difference-frequency generation of an amplified 1.5 microm diode laser and a cw Tm-doped fiber laser in orientation-patterned (OP) GaAs has been developed and evaluated for spectroscopic applications. The source can be tuned to any frequency in the 7.6-8.2 microm range with an output power of 0.5 mW. The measured characteristics of the OP-GaAs sample demonstrate a high quality of the material.     

Altering the Remote Past

An abstract treatment of Bell inequalities in proposed, in which the parameters characterizing Bell's observable can be times rather than directions. The violation of a Bell inequality might then be taken to mean that a property of a system can be changed by the timing of a distant measurement, which could take place in the future.     

Janossy Densities. I. Determinantal Ensembles

We derive an elementary formula for Janossy densities for determinantal point processes with a finite rank projection-type kernel. In particular, for =2 polynomial ensembles of random matrices we show that the Janossy densities on an interval I can be expressed in terms of the Christoffel–Darboux kernel for the orthogonal polynomials on the complement of I.     

Nonlinear Maxwell Equations in Inhomogeneous Media

We study the basic properties of the Maxwell equations for nonlinear inhomogeneous media. Assuming the classical nonlinear optics representation for the nonlinear polarization as a power series, we show that the solution exists and is unique in an appropriate space if the excitation current is not too large. The solution to the nonlinear Maxwell equations is represented as a power series in terms of the solution of the corresponding linear Maxwell equations. This representation holds at least for the time period inversely proportional to the appropriate norm of the solution to the linear Maxwell equation. We derive recursive formulas for the terms of the power series for the solution including an explicit formula for the first significant term attributed to the nonlinearity.     

Specific Interaction of Coproporphyrin I with Antibodies in Water and Reverse Micelles: Dimerization of Antibodies Affects Antigen Binding Site

The antigen-antibody interaction between coproporphyrin I and anti-coproporphyrin antibodies was studied by a fluorescence method in water and a reverse micellar system: n-octane/Aerosol OT. Coproporphyrin fluorescence was quenched, and coproporphyrin emission maximum was shifted to the long-wavelength region after binding to the antibodies or Fab-fragments. The mechanism of this quenching is static, most probably, by a tryptophan residue (or maybe lysine or methionine). Apparent dynamic quenching, in this case, arises from protein backbone motion. A special kind of antibody Fab-Fab dimerization was proposed.     

End-to-end correlation for a C-12 hydrocarbon chain

The 19F nuclear spin-lattice relaxation rate constants were measured as a function of magnetic field strength for 1,12-diaminododecane labeled at one end with a nitroxide radical and at the other with a trifluoromethyl group. The magnetic relaxation dispersion profile (MRD) reports the spectral density function appropriate to the end-to-end correlation function for the doubly labeled molecule. After extrapolation to zero concentration to eliminate the intermolecular relaxation contribution to relaxation, the resulting intramolecular MRD profile was compared with several model approaches. The rotational model for the spectral density functions as included in the Solomon-Bloembergen-Morgan equations does not describe the data well. The earlier model of Freed for nuclear spin relaxation induced by a freely diffusing paramagnetic co-solute is not rigorous for this case because the paramagnet is tethered to the observed nuclear spin and only a restricted space in the immediate vicinity of the nuclear spin is accessible for pseudo-translational diffusion of one end of the molecule with respect to the other. A generalization of the Torrey model for magnetic relaxation by translational diffusion developed by Nevzorov and Freed, which includes the effect of restrictions imposed by the finite length of the chain, describes the experiment within experimental errors. A simple modification of the Hwang-Freed model that does not specifically include the dynamical effects of the finite tether also provides a good approximation to the data when the tether chain is sufficiently long.     

Optical metrics and birefringence of anisotropic media

The material tensor of linear response in electrodynamics is constructed out of products of two symmetric second rank tensor fields which in the approximation of geometrical optics and for uniaxial symmetry reduce to “optical” metrics, describing the phenomenon of birefringence. This representation is interpreted in the context of an underlying internal geometrical structure according to which the symmetric tensor fields are vectorial elements of an associated two-dimensional space.     

Charge transfer from ammonia physisorbed on nanotubes

We report the use of nanotube field-effect transistor devices for chemical sensing in a conducting liquid environment. Detection of ammonia occurs through the shift of the gate voltage dependence of the source-drain current. We attribute this shift to charge transfer from adsorbed ammonia molecules, with the amount of charge estimated to be as small as 40 electrons for the smallest shift detected. Using the concentration dependence of the response as an adsorption isotherm, we are able to measure the amount of charge transfer to be 0.04 electron per ammonia molecule.