Research on adaptive temperature control in sound field induced by self-focused concave spherical transducer

Temperature control of hyperthermia treatments is generally implemented with multipoint feedback system comprised of phased-array transducer, which is complicated and high cost. Our simulations to the acoustic field induced by a self-focused concave spherical transducer (0.5 MHz, 9 cm aperture width, 8.0 cm focal length) show that the distribution of temperature can keep the same “cigar shape” in the focal region during ultrasound insonation. Based on the characteristic of the temperature change, a two-dimensional model of a “cigar shape” tumor is designed and tested through numerical simulation. One single-point on the border of the “cigar shape” tumor is selected as the control target and is controlled at the temperature of 43 °C by using a self-tuning regulator (STR). Considering the nonlinear effects of biological medium, an accurate state-space model obtained via the finite Fourier integral transformation to the bioheat equation is presented and used for calculating temperature. Computer simulations were performed with the perfusion rates of 2.0 kg/(m³ s) and 4.5 kg/(m³ s) to the different targets, it was found that the temperatures on the border of the “cigar shape” tumor can achieve the desired temperature of 43 °C by control of one single-point. A larger perfusion rate requires a higher power output to obtain the same temperature elevation under the same insonation time and needs a higher cost for compensating the energy loss carried away by blood flow after steady state. The power output increases with the controlled region while achieving the same temperature at the same time. Especially, there is no overshoot during temperature elevation and no oscillation after steady state. The simulation results demonstrate that the proposed approach may offers a way for obtaining a single-point, low-cost hyperthermia system.     

Optimal pulse width modulation for sinusoidal fringe generation with projector defocusing

Recently, a study showed that generating sinusoidal fringe patterns by properly defocusing binary ones can significantly simplify three-dimensional shape measurement system development and drastically improve its speed. However, when the fringe stripes are very wide, it is very difficult for this technique to achieve high-quality measurement. This Letter presents a method to improve this technique by selectively eliminating high-frequency harmonics induced by a squared binary pattern. As a result, better sinusoidal fringe patterns can be generated with a small degree of defocusing even for wide fringe stripes. Simulation and experiments will be presented to verify the performance of this proposed technique.     

Temperature- and pH-dependent morphology and FT-IR analysis of magnesium carbonate hydrates

Various morphologies of magnesium carbonate hydrates have been synthesized by carefully adjusting the reaction temperature and pH value of the initial reaction solution in the precipitation process. At lower temperatures (from room temperature to 328 K) and lower pH values (variation with the reaction temperature), magnesium carbonate hydrates are prone to display needlelike morphology, and the axis diameter of the particles decreases with the increase of reaction temperature and pH value. With the further increase of the reaction temperature (333-368 K) and pH value, the sheetlike crystallites become the preferred morphology, and at higher temperatures and pH values, these crystallites tend to assemble into layerlike structures with diverse morphologies, such as spherical-like particles with rosette-like structure and cakelike particles built from sheetlike structure. Fourier transform infrared (FT-IR) spectra show that these various morphologies are closely related to their compositions. The needlelike magnesium carbonate hydrate has a formula of MgCO3.xH2O, in which the value x is greatly affected by the experimental conditions, whereas with the morphological transformation from needlelike to sheetlike structure, their corresponding compositions also change from MgCO3.xH2O to Mg5(CO3)4(OH)2.4H2O in the interval of 328-333 K.     

Two definite integrals involving products of four Legendre functions

The definite integrals \( \int _{-1}^1x[P_\nu (x)]^4\mathrm{d}x\) and \( \int _{0}^1x[P_\nu (x)]^2\{[P_\nu (x)]^2-[P_\nu (-x)]^2\}\mathrm{d}x\) are evaluated in closed form, where \( P_\nu \) stands for the Legendre function of degree \( \nu \in \mathbb C\). Special cases of these integral formulae have appeared in arithmetic studies of automorphic Green’s functions and Epstein zeta functions.     

Enzyme encapsulation in nanoporous silica spheres

Encapsulating enzymes in mesoporous silica spheres via immobilization, followed by assembling an organic/inorganic nanocomposite shell on the particle surface leads to high loadings, high enzymatic activity and stability, and protection from proteolysis.     

原子转移自由基聚合合成(甲基)丙烯酸酯类模型聚合物及其动力学研究

本文采用一种新颖的活性自由基聚合—原子转移自由基聚合（ＡＴＲＰ）的方法，以１－溴代苯乙烷作为引发剂，过渡金属卤化物与配位剂络合物（ＣｕＢｒ／２，２’－联吡啶）为催化体系，环己酮为溶剂，进行了甲基丙烯酸正丁酯（ＢＭＡ）和丙烯酸正丁酯（ＢＡ）的活性聚合。得到具有指定分子量和窄分子量分布（１．２＜Ｍｗ／Ｍｎ＜１．５）的模型聚合物。计算并讨论了两聚合体系的ＡＴＲＰ的动力学数据     

Theoretical analysis of adhering lipid vesicles with free edges

A theoretical model for describing the adhesion of lipid vesicle with free edges is developed. For adhesion in contact potential or in finite-range potential, the total energy functional is defined as the sum of elastic free energy, the surface energy, the line tension energy and the contact potential or the long-ranged potential. The equilibrium differential equation and boundary conditions for opening-up lipid vesicles are derived through minimizing the total energy functional. Numerical solutions to these equations are obtained under the axial symmetric condition. These numerical solutions can be used to qualitatively explain the influence of the substrate on the open-up lipid vesicles.     

Light beams with flat-topped profiles

A necessary condition for generating optical beams with a nearly uniform profile at a certain transverse plane is proposed. This proposal leads to the introduction of a set of light beams with flat-topped profiles. This set of beams can be expressed as a finite series of lowest-order Gaussian modes (TEM(00)) with different parameters. The main features of this set of beams are investigated and compared with those predicted by existing models of flattened Gaussian beams.     

Synthesis of silver nanoparticles via electrochemical reduction on compact zeolite film modified electrodes

Monodisperse silver nanoparticles with different sizes were synthesized by electrochemical reduction inside or outside zeolite crystals according to the silver exchange degree of compact zeolite film modified electrodes.